| Model era table (Premier / Multivox model numbers) | late 1930s-late 1960s | 14 | Era dating only: Premier re-used model numbers across decades and re-badged Multivox designs. |
| Company history era (Sorkin / Multivox) | late 1930s-1974 | 5 | Context for interpreting the branding; not a date by itself. |
| EIA component codes (pots, transformers, Jensen speakers) | late 1930s-1960s | 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 |