| Model + version era table (EH / BR / GA / GSS / THOR / G series) | 1935-1975 (plus 1999-2011 reissues) | 63 | Era, not unit date: GA model numbers were re-used across versions with different tube sets (e.g. GA-40 Les Paul first version 1952-54 vs second versio |
| Transformer code (7 digits = maker + year + week) | all eras | 0 | 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 |
| Jensen speaker code under the magnet bell cover | 1950s-1960s | 1 | 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 |
| Potentiometer source-date codes | all eras | 1 | 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" |