| Cabinet/panel/covering eras (a fast era check) | 1966-1980s, and 1994-present | 6 | Cosmetics were sometimes re-covered, so use with the serial chart. |
| Model number system (K + power + configuration digit) | 1966-1972 (power figures), all eras (configuration digit) | 9 | Model identification, not dating — but it tells you which era the power number belongs to (doubled figures only work 1966-1972) and what the amp actua |
| Cabinet numbering (speaker count/size + brand letter + head unit) | 1966-1975 | 2 | Identification aid; the date still comes from the cabinet serial (+45000 offset rule). |
| EIA component codes (transformers, pots, speakers) | 1965-1980 | 3 | 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 |