| System | Period | Rows | What it dates |
|---|---|---|---|
| Tube chart date code (vintage + reissue) | vintage 1951–1969 · reissue 1990–2015 | 540 | |
| QA sticker date code | 1990 to today | 3 | |
| EIA transformer code | whole vintage era | 8 | |
| EIA speaker code | 1946 to today | 8 | |
| Potentiometer date code | whole vintage era | 5 | |
| Chassis ink date stamp | mid-1960s – early 1980s | 3 | |
| Circuit code (era marker) | 1963 to today | 59 |