| Metal plate vs foil sticker (which numbering system applies) | 1941-1968 | 0 | All numbers are approximate matches; the plate type must be checked before decoding. |
| Gretsch amp model era table (model number series) | early 1950s-1970s, plus 2005-2009 reissues | 23 | Era, not unit date; combined with the plate type and the Valco table it narrows the window. |
| EIA component codes | 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 |