| System | Period | Rows | What it dates |
|---|---|---|---|
| Two-character serial prefix (year digit + product type), 1975-1989 | late 1975 - 1989 (dropped after 1989; '00-' = 1990 or later) | 15 | Dates the product by its own factory numbering (not a component), so it is the strongest Peavey witness — but only if the prefix format is intact. A n |
| EIA source-date codes on transformers / speakers / pots | all eras | 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 |