[Arran]

Mike,
The bayonet based '01As are not like UX199s compared to UV199s, where they have different pinouts, they are the same electrically as the UV versions, just with longer pins. in fact many sets in the 1924-25 era had bayonet sockets, but they left the dealer with UV201As in them, with the locking pin. I'm not sure when they discontinued making UX based tubes, but I read that A.K quit using them because the four pin UV style sockets were cheaper, so the late model 20C sets had four pin sockets like an #80 would use, the one I inherited from my late uncle used bayonet style sockets, but with UV tubes in the sockets, including some ST style '01As, again with the side pin.
Regards
Arran