With diaphragms that age, fatigue is likely to be the reason for difference, not different types.
Minor manufacturing differences, even slight tolerance differences, can amplify to possibly audible differences 50+ years later.
I'd say they will be part number 20275 diaphragms, the 16 ohm 1 inch.

The point? Do they sound great to you? If yes, then who cares what someone else thinks.