Loudspeakers carry the most consistently readable date code in a vintage amp: maker, year and week, usually on the rim of the basket at the back.
The code is the familiar EIA source-date form: a manufacturer number, then the year, then the week. Speaker makers used by the amps in this reference include 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.
The code sits on the basket rim on most drivers and on the magnet cover of some Jensen units. On Gibson combos it can be stamped under the magnet bell cover, which has to come off to read it.
British amps use Celestion date codes instead, and those change form between eras, with the Type 2 codes read in reverse order. Vox adds a practical rule: allow at least three to four weeks after the speaker date for assembly, testing and the serial number.
A speaker code dates the speaker. If a driver was replaced its code is newer than the amp, and on a combo with one original driver that code is often the only dated original part left.
Basket rim first, and on Jensen units check the magnet cover as well.
Three parts in that order, with separators varying by maker.
A single year digit leaves the decade open until the model or another code decides.
For Vox and other British amps, add three to four weeks to the speaker date.
A driver whose maker does not match the era suggests a replacement.
1946 to today · 8 rows · confidence High · Blue Book of Guitar Values — dating tools (PDF)
| Code as marked | Meaning | Source |
|---|---|---|
| 220022 | 1950–1960 | Blue Book of Guitar Values — dating tools (PDF) |
| 465-831 | 1958–1968 | Blue Book of Guitar Values — dating tools (PDF) |
| 677145 | 1971 | Blue Book of Guitar Values — dating tools (PDF) |
| 220 7001 | 1970 | guitarhq — pot & EIA date codes |
| 285709 | 1957 | guitarhq — pot & EIA date codes |
| 137341 | 1953 | guitarhq — pot & EIA date codes |
| 220 8 20 | 1958 | Hendrix Guitars — Fender & Vox date codes |
| 4656755 | guitarhq — pot & EIA date codes |
| EIA code | Maker | Notes |
|---|---|---|
| 220 | Jensen | |
| 465 | Oxford | |
| 137 | CTS (Chicago Telephone Supply) | |
| 328 | Utah | |
| 285 | Rola | |
| 67 | Eminence | |
| 73 | J.B. Lansing (JBL) | |
| 391 | Altec-Lansing | |
| 433 | Cleveland | |
| 649 | Electro-Voice (EV) | |
| 1098 | Pyle | |
| 109 | ||
| 117 | Credence Speakers | |
| 575 | Heppner | |
| 918 | Oaktron | |
| 1279 | WeberVST | |
| 550 | Valco / National / Supro / Airline / Oahu |
1944 to today · 23 rows · confidence Medium · Bygone Tones — Celestion date codes & Plexi checks
1960–1967 · 89 rows · confidence Medium · Vox AC30 — dateable amplifiers register — dateable AC30/AC15 list
1950s-1960s · 1 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. On Gibson combos the speaker is frequently the only original dated part left.
| Code as marked | Meaning | Source |
|---|---|---|
| 220616 | 1956 — Jensen, 16th week — the year digit is ambiguous (1956 or 1966); the forum thread resolved this GA-40 as a 1956 by cosmetics. 'Reported' community point, unofficial. | Les Paul Forum — GA-40 dating thread |
| EIA code | Maker | Notes |
|---|---|---|
| 220 | Jensen |
The EIA source-date form: manufacturer number, year and week, most often on the basket rim of the frame.
By era: the letter and digit pairs change form, and the Type 2 codes read in the reverse order.
No. It dates the speaker, and on a British amp you should allow three to four weeks or more before the finished amplifier was tested and numbered.