That was true when it was a simple screw mout with one pin to close the lens down.It wasn’t a problem back in the 50’s and 60’s when m42 screw mount was almost universal , and people did mix and match lenses .
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With kind regards
Derek.
Once some sort of automation started we then had different versions of the screw mount, not fully compatible with each other.
Pentax had the ES, Fujica had the ST, Praktica had the PL and EE, Ricoh the TLS EE, Olympus the FTL and Exakta (Petri made) had their own version too.
The reason why there were then more than 20 brands selling K mount bodies was that there was no copyright fee and they were all made by a few brands only, mostly Ricoh and Cosina, and then re-badged as somethig else.