| Model + front panel + logo era table (the primary Orange dating key) | 1968-1979 | 24 | This table dates the model/era, not a specific unit: transitional amps exist (documented example — a 1979 Series II Super Bass on a 1974 OR120 chassis |
| Dated example units (serial -> evidence) | 1969-1978 | 27 | Single observations ('reported'), not a table: treat as corroboration, not as a rule. |
| Cabinet serial - first digit as a rough year | 1968-1979 | 3 | Explicitly a heuristic: 'it's not a guarantee. I have also seen some that don't make sense at all.' Also note the head-shell vent panel number is NOT |
| Inspection tag inside the chassis | 1969-1979 | 3 | Present only on part of the production run; the tag dates inspection, which is extremely close to (but not identical with) completion. |
| Matamp-built vs Orange-built chassis (needed before the year chart is applied) | 1968-1975 | 7 | Identification only — it narrows the year window through the era table, it does not date the unit. Transformer brands are the most reliable tell. |
| Cabinet cosmetics era (badges, tolex, handles, corners) | 1968-1979 | 9 | Cosmetics can be replaced; use together with the speaker date codes, which are the best witness. |
| EIA/date codes on capacitors, pots and speakers (Corroboration layer) | 1968-1979 and later | 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 |