| System | Period | Rows | What it dates |
|---|---|---|---|
| Model code (series / power) | 1965 to today | 14 | |
| Country letter in the serial | 1997 to today | 4 | |
| Voltage letter in the serial | 1997 to today | 7 | |
| Celestion speaker date code | 1944 to today | 23 | |
| Transformer suppliers: Drake → Dagnall | 1965–1972 | 14 | |
| Plexi cosmetics by year | 1965–1969 | 12 |