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Code system

EIA component date codes

Almost every vintage amp contains at least one part stamped with its manufacturer, year and week. That code is the fallback when the maker's own numbering does not date the amplifier.

The EIA source-date code is a manufacturer number followed by the year and the week: 606-4-21 is a Schumacher transformer from the 21st week of 1964, and 1376623 is a CTS pot from the 23rd week of 1966. Separators vary, and some makers print the same digits without them.

Manufacturer numbers matter as much as the dates. Speakers: Jensen 220, Oxford 465, CTS 137, Utah 328, Quam 270, Rola 285, Altec/Lansing 391, Electro-Voice 649, Eminence 67, Cleveland 433 and Pyle 1098. Transformers: 606 Schumacher, 138 Stancor, 830 Triad, 831 Better Coil and 549 Midwest Coil among them. Pots and capacitors: 137 CTS, 304 Stackpole, 140 Clarostat, 235 Mallory and 834 Mel Rain.

A component code dates the part, not the amp. A replaced transformer carries a code newer than the amp, and a pot or capacitor can be date-coded ahead of use, so the code can also be later than the build. Transformers and speakers are the strongest witnesses in this family; pots and capacitors are the weakest.

Short codes carry a decade trap: 606-4-21 could be 1964 or 1974, and Jensen's 220-27 could be 1951 or 1961, because the year is printed as a single digit.

How to read it
01 / Identify the part

Decide whether the code is on a transformer, a speaker, a pot or a capacitor, because that sets the confidence.

02 / Split the code

Read manufacturer, then year, then week. Where the year is a single digit, keep both decades as candidates.

03 / Name the manufacturer

Use the manufacturer number to identify the supplier, which also shows which suppliers a maker used in a given era.

04 / Decide the decade

Fix the decade with the model, the cosmetics or another code, never with the short code alone.

05 / Collect a second code

Two independent original parts agreeing on a year is the strongest combination available when there is no assembly sticker.

06 / Apply the upper-bound rule

The amp is not older than its newest original part, so the latest agreed code is a floor rather than a birthday.

Traps
Try it
Add the model or a cosmetic detail (optional — it removes guesswork)
Tables in the archive

Fender — EIA transformer code

whole vintage era · 8 rows · confidence High · Blue Book of Guitar Values — Fender transformer date codes

Code as markedMeaningSource
606-4-211964, week 21Blue Book of Guitar Values — Fender transformer date codes
606-66-361966, week 36Blue Book of Guitar Values — Fender transformer date codes
606 4 321964, week 32Hendrix Guitars — Fender & Vox date codes
606-6451966–1976Vintage Fender Amp Repair — date codes
606-6-271956–1966True Vintage Guitar — dating a Fender amp
549-62211962, week 21Blue Book of Guitar Values — dating tools (PDF)
140-64211964, week 21Blue Book of Guitar Values — dating tools (PDF)
8311966–1968ggjaguar — Fender amp research (Gagliano series) — Part 5
Manufacturers
EIA codeMakerNotes
138Stancor (Chicago-Standard)
606Woodward-Schumacher
830Triad
831Better Coil & Transformer
239Merit Coil & Transformer
394Foster Transformer
412General Transformer
418United Transformer Corp (UTC)
524Triwec Transformer
549Midwest Coil & Transformer
757Grand Transformers
776Ogden Coil & Transformer
892American Transformer
928Acme Coil & Transformer
141Coil Engineering
172Ensign Coil
183Freed
194General Radio
218Jefferson Electric
238Thordarsen-Meissner
305Standard Coil
352Essex (Transformer Division)
366New York Transformer
391Altec-Lansing / Peerless
452Empire Coil
489Radio-Television Products Corp
503Caledonia
550Standard Winding Company
572F&V Coil Winding
637Central Coil
682Electrical Windings
773Forest Electric
843Klipsch
878Acro Products (Acrosound)
883Mohawk
897Tresco
906Coilcraft
908Aerocoil
933Magnetic Coil Manufacturing
934Oaktron
1005Northlake
1052Pacific
106Allen-Bradley
134CentraLab
137CTS (Chicago Telephone Supply)
140Clarostat
304Stackpole
381Bourns Networks
615IRC (International Resistive Company)

Ampeg — EIA component codes (speakers, transformers, pots, capacitors)

whole vintage era · 16 rows · confidence Medium · Found Sound (Ampeg & Mesa dating guides)

Code as markedMeaningSource
137634CTSFound Sound (Ampeg & Mesa dating guides)
220JensenFound Sound (Ampeg & Mesa dating guides)
137CTSFound Sound (Ampeg & Mesa dating guides)
67EminenceFound Sound (Ampeg & Mesa dating guides)
270QuamFound Sound (Ampeg & Mesa dating guides)
285RolaFound Sound (Ampeg & Mesa dating guides)
391AltecFound Sound (Ampeg & Mesa dating guides)
649Electro-VoiceFound Sound (Ampeg & Mesa dating guides)
878AcrosoundFound Sound (Ampeg & Mesa dating guides)
138StancorFound Sound (Ampeg & Mesa dating guides)
682Electrical WindingsFound Sound (Ampeg & Mesa dating guides)
926Todd Electric Co.Found Sound (Ampeg & Mesa dating guides)
668Standard Electric ProductsFound Sound (Ampeg & Mesa dating guides)
472PyramidFound Sound (Ampeg & Mesa dating guides)
34Cornell-DubilierFound Sound (Ampeg & Mesa dating guides)
304StackpoleFound Sound (Ampeg & Mesa dating guides)
Manufacturers
EIA codeMakerNotes

Vox — EIA component codes in Vox

whole era · 2 rows · confidence Medium · Vox Showroom — dating Vox equipment

Code as markedMeaningSource
13766231966, week 23 · CTSVox Showroom — dating Vox equipment
235-70171970, week 17 · MalloryVox Showroom — dating Vox equipment
Manufacturers
EIA codeMakerNotes
137CTS
235Mallory

Gibson (amps) — Transformer code (7 digits = maker + year + week)

all eras · 0 rows · confidence Low · Gibson forum — GA-series dating threads

Component codes date the PART, not the amp: a replaced transformer/speaker/pot can be newer than the amp. Upper-bound rule — the amp is not older than its newest ORIGINAL component; several independent codes must agree (2+) where no assembly sticker exists.

Manufacturers
EIA codeMakerNotes
138Stancor
606Schumacher

Peavey — EIA source-date codes on transformers / speakers / pots

all eras · 1 rows · confidence Medium · guitarhq — pot & EIA date codes

Component codes date the PART, not the amp: a replaced transformer/speaker/pot can be newer than the amp. Upper-bound rule — the amp is not older than its newest ORIGINAL component; several independent codes must agree (2+) where no assembly sticker exists. Pots and capacitors are often date-coded AHEAD of use (CTS by a month or two; post-dates up to 18 months are documented, distributors returned "stale" batches) — a pot code alone must never be the only witness of a build year (guitarhq).

Code as markedMeaningSource
137 66231966 — CTS, 23rd week of 1966 — worked example of the format (Vox/CTS example kept here because it is the same EIA system)Vox Showroom — dating Vox equipment
Manufacturers
EIA codeMakerNotes
220Jensen
465Oxford
137CTS
328Utah
270Quam
285Rola
391Altec/Lansing
649Electro-Voice
67Eminence
433Cleveland
1098Pyle
117Credence
682Electrical Windings
304Stackpole
235Mallory

Silvertone (Danelectro / Sears) — EIA component codes (speakers, transformers, pots)

1940s-1968 · 3 rows · confidence Medium · Silvertone World — model 1484

Component codes date the PART, not the amp: a replaced transformer/speaker/pot can be newer than the amp. Upper-bound rule — the amp is not older than its newest ORIGINAL component; several independent codes must agree (2+) where no assembly sticker exists. Pots and capacitors are often date-coded AHEAD of use (CTS by a month or two; post-dates up to 18 months are documented, distributors returned "stale" batches) — a pot code alone must never be the only witness of a build year (guitarhq).

Code as markedMeaningSource
185.110401484 chassis plate; the same page documents the amp's Jensen 12 in. speakers with a Danelectro factory stamping indicating a mid-July 1964 buildSilvertone World — model 1484
pots dated June 1966June 1966 — 1485 pots; the 1485's own window is 1963-1966, so the pot date sits at the very end of the runSilvertone World — model 1485
1962 stamping (1472)1962 — a 1962 stamping photographed inside a 1472 (the model ran Fall/Winter 1961 - Spring/Summer 1963)Silvertone World — model 1472
Manufacturers
EIA codeMakerNotes
220Jensen
465Oxford
137CTS
328Utah
270Quam
285Rola
391Altec/Lansing
649Electro-Voice
67Eminence
433Cleveland
1098Pyle
117Credence
185Danelectro (chassis/service plate prefix)

Mesa/Boogie — EIA source-date codes on components

all eras · 0 rows · confidence Low · Schematic Heaven — date codes

Component codes date the PART, not the amp: a replaced transformer/speaker/pot can be newer than the amp. Upper-bound rule — the amp is not older than its newest ORIGINAL component; several independent codes must agree (2+) where no assembly sticker exists. Pots and capacitors are often date-coded AHEAD of use (CTS by a month or two; post-dates up to 18 months are documented, distributors returned "stale" batches) — a pot code alone must never be the only witness of a build year (guitarhq).

Manufacturers
EIA codeMakerNotes
220Jensen
465Oxford
137CTS
328Utah
270Quam
285Rola
391Altec/Lansing
649Electro-Voice
67Eminence
433Cleveland
1098Pyle
117Credence

Gretsch (amps) — EIA component codes

all eras · 0 rows · confidence Low · guitarhq — pot & EIA date codes

Component codes date the PART, not the amp: a replaced transformer/speaker/pot can be newer than the amp. Upper-bound rule — the amp is not older than its newest ORIGINAL component; several independent codes must agree (2+) where no assembly sticker exists. Pots and capacitors are often date-coded AHEAD of use (CTS by a month or two; post-dates up to 18 months are documented, distributors returned "stale" batches) — a pot code alone must never be the only witness of a build year (guitarhq).

Manufacturers
EIA codeMakerNotes
220Jensen
465Oxford
137CTS
328Utah
270Quam
285Rola
391Altec/Lansing
649Electro-Voice
67Eminence
433Cleveland
1098Pyle
117Credence

Magnatone (Estey) — EIA component codes (speakers, capacitors, transformers)

1940s-1960s · 2 rows · confidence Low · Vintage Guitar magazine

Component codes date the PART, not the amp: a replaced transformer/speaker/pot can be newer than the amp. Upper-bound rule — the amp is not older than its newest ORIGINAL component; several independent codes must agree (2+) where no assembly sticker exists. Pots and capacitors are often date-coded AHEAD of use (CTS by a month or two; post-dates up to 18 months are documented, distributors returned "stale" batches) — a pot code alone must never be the only witness of a build year (guitarhq). The Vintage Guitar history shows the method in use — an early amp dated by its pot code — and also shows its limits: on another example 'too much has been changed on this M-192's insides to trust the 1951 pot codes or the 1953 speaker code'.

Code as markedMeaningSource
pot code dated late 19481948 — three-tube single 8 in. K&H-branded pre-Magna amp — the pot code places it in late 1948 (author's own observation, Vintage Guitar)Vintage Guitar magazine
1951 pot codes / 1953 speaker code (M-192)recorded by the source as NOT trustworthy on that particular amp because too much had been changedVintage Guitar magazine
Manufacturers
EIA codeMakerNotes
220Jensen
465Oxford
137CTS
328Utah
270Quam
285Rola
391Altec/Lansing
649Electro-Voice
67Eminence
433Cleveland
1098Pyle
117Credence

Sunn — EIA component codes (transformers, pots, speakers)

1965-1980 · 0 rows · confidence Low · guitarhq — pot & EIA date codes

Component codes date the PART, not the amp: a replaced transformer/speaker/pot can be newer than the amp. Upper-bound rule — the amp is not older than its newest ORIGINAL component; several independent codes must agree (2+) where no assembly sticker exists. Pots and capacitors are often date-coded AHEAD of use (CTS by a month or two; post-dates up to 18 months are documented, distributors returned "stale" batches) — a pot code alone must never be the only witness of a build year (guitarhq).

Manufacturers
EIA codeMakerNotes
220Jensen
465Oxford
137CTS
328Utah
270Quam
285Rola
391Altec/Lansing
649Electro-Voice
67Eminence
433Cleveland
1098Pyle
117Credence

Standel — EIA component codes

1950s-1970s · 0 rows · confidence Low · guitarhq — pot & EIA date codes

Component codes date the PART, not the amp: a replaced transformer/speaker/pot can be newer than the amp. Upper-bound rule — the amp is not older than its newest ORIGINAL component; several independent codes must agree (2+) where no assembly sticker exists. Pots and capacitors are often date-coded AHEAD of use (CTS by a month or two; post-dates up to 18 months are documented, distributors returned "stale" batches) — a pot code alone must never be the only witness of a build year (guitarhq). On a hand-built amp restorers note that a single code can be the only surviving original part, so two independent codes should agree.

Manufacturers
EIA codeMakerNotes
220Jensen
465Oxford
137CTS
328Utah
270Quam
285Rola
391Altec/Lansing
649Electro-Voice
67Eminence
433Cleveland
1098Pyle
117Credence

Premier (Multivox) — EIA component codes (pots, transformers, Jensen speakers)

late 1930s-1960s · 0 rows · confidence Low · Blue Book of Guitar Values — premier

Component codes date the PART, not the amp: a replaced transformer/speaker/pot can be newer than the amp. Upper-bound rule — the amp is not older than its newest ORIGINAL component; several independent codes must agree (2+) where no assembly sticker exists. Pots and capacitors are often date-coded AHEAD of use (CTS by a month or two; post-dates up to 18 months are documented, distributors returned "stale" batches) — a pot code alone must never be the only witness of a build year (guitarhq).

Manufacturers
EIA codeMakerNotes
220Jensen
465Oxford
137CTS
328Utah
270Quam
285Rola
391Altec/Lansing
649Electro-Voice
67Eminence
433Cleveland
1098Pyle
117Credence

Traynor — EIA codes on filter capacitors and circuit breakers

1960s-1970s · 3 rows · confidence Medium · 0rigami — Traynor dates

Component codes date the PART, not the amp: a replaced transformer/speaker/pot can be newer than the amp. Upper-bound rule — the amp is not older than its newest ORIGINAL component; several independent codes must agree (2+) where no assembly sticker exists. Pots and capacitors are often date-coded AHEAD of use (CTS by a month or two; post-dates up to 18 months are documented, distributors returned "stale" batches) — a pot code alone must never be the only witness of a build year (guitarhq).

Code as markedMeaningSource
235-7051Y1970 — Mallory EIA 235, 51st week of 19700rigami — Traynor dates
834-73051973 — Mel Rain Corp EIA 834, 5th week of 19730rigami — Traynor dates
834-73281973 — Mel Rain Corp EIA 834, 28th week of 19730rigami — Traynor dates
Manufacturers
EIA codeMakerNotes
235Mallory
834Mel Rain Corp

Kustom — EIA component codes (transformers, pots, speakers)

1965-1980 · 3 rows · confidence Medium · Vintage Kustom — collector forum & charts

Component codes date the PART, not the amp: a replaced transformer/speaker/pot can be newer than the amp. Upper-bound rule — the amp is not older than its newest ORIGINAL component; several independent codes must agree (2+) where no assembly sticker exists. Pots and capacitors are often date-coded AHEAD of use (CTS by a month or two; post-dates up to 18 months are documented, distributors returned "stale" batches) — a pot code alone must never be the only witness of a build year (guitarhq).

Code as markedMeaningSource
43001 10057341967 — transformer stamp quoted on the chart's forum thread: 'the transformer places the amp's birth at the 34rd week of 1967' (SN 19508, K200A-1)Vintage Kustom — collector forum & charts
019-7002-011970 — transformer date code quoted for SN 41549 (K-100-2), read by the chart's author as 'a very early 1970'Vintage Kustom — collector forum & charts
137 7349CTS speaker code seen in a Kustom 2-15 cabinet; the chart's author notes CTS was the baseline bass driver brandVintage Kustom — collector forum & charts
Manufacturers
EIA codeMakerNotes
220Jensen
465Oxford
137CTS
328Utah
270Quam
285Rola
391Altec/Lansing
649Electro-Voice
67Eminence
433Cleveland
1098Pyle
117Credence
137CTS

Hiwatt — Component date codes ('YY WW' or 'WW YY' on caps / pots / speakers)

1966-1984 · 8 rows · confidence Medium · hiwatt.org — Hiwatt dates & history

Component codes date the PART, not the amp: a replaced transformer/speaker/pot can be newer than the amp. Upper-bound rule — the amp is not older than its newest ORIGINAL component; several independent codes must agree (2+) where no assembly sticker exists. The source adds the stock-lag caveat explicitly: 'The parts were likely manufactured one to twelve months (sometimes longer) before being used to build an amp or fill a speaker cabinet.'

Code as markedMeaningSource
cap can 20th week 19691969 — photographed examplehiwatt.org — Hiwatt dates & history
cap can 48th week 19691969 — photographed examplehiwatt.org — Hiwatt dates & history
cap can 14th week 19711971 — photographed examplehiwatt.org — Hiwatt dates & history
pot 47th week 19681968 — photographed examplehiwatt.org — Hiwatt dates & history
pot 37th week 19731973 — photographed examplehiwatt.org — Hiwatt dates & history
speaker 51st week 19711971 — photographed examplehiwatt.org — Hiwatt dates & history
speaker 31st week 19711971 — photographed examplehiwatt.org — Hiwatt dates & history
speaker 13th week 19771977 — photographed examplehiwatt.org — Hiwatt dates & history

Orange — EIA/date codes on capacitors, pots and speakers (Corroboration layer)

1968-1979 and later · 0 rows · confidence Medium · Vintage Orange Amplification — technical info

Component codes date the PART, not the amp: a replaced transformer/speaker/pot can be newer than the amp. Upper-bound rule — the amp is not older than its newest ORIGINAL component; several independent codes must agree (2+) where no assembly sticker exists. Pots and capacitors are often date-coded AHEAD of use (CTS by a month or two; post-dates up to 18 months are documented, distributors returned "stale" batches) — a pot code alone must never be the only witness of a build year (guitarhq). Orange adds: 'If your amplifier has the original capacitors in them, you can also get a rough build year based on those dates.'

Manufacturers
EIA codeMakerNotes
220Jensen
465Oxford
137CTS
328Utah
270Quam
285Rola
391Altec/Lansing
649Electro-Voice
67Eminence
433Cleveland
1098Pyle
117Credence
Frequently asked
What does an EIA code look like?

A manufacturer number plus a year and a week: 606-4-21 is Schumacher week 21 of 1964, and 1376623 is CTS week 23 of 1966.

Which component gives the best date?

A transformer or a speaker, because both are date-coded at manufacture and are less likely to have been replaced. Pots and capacitors are the weakest witnesses.

Why do some codes show only one year digit?

Because the manufacturer printed a short form. The decade then has to come from the model, the cosmetics or a second code.

Does an EIA code date my amp?

It dates the part. The amp is never older than its newest original part, so component codes set a floor rather than a birthday.

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