Originally posted by boriscleto My Super-Tak 50/1.4 8-element from 1964 has JIS screws.
Interesting, I have not seen those screws in a lens of that age.
Anyway, one anecdote is only OK for politicians, not for science! So for proof, I offer 4 anecdotes.
First is two K55/1.8s. On the left, both kinds of screws, on the right, just JIS:
Next, a Super Takumar 135/3.5. I don't know its exact age but it's the 4/4 formula so it's the newer 135/3.5 formula. Another mixture:
The third lens is my Super-Takumar 85mm f1.9, with the old font style. So almost relevant to the topic.
Last, an SMC Takumar 55mm f2.0:
I still like my huge parts bin theory, but we'll never take enough lenses apart for a statistically significant answer.