In article ,
e says...

Don, the standard is .800"-36TPI, 55 degree Whitworth threads, has
been for over 100 years. The same thread is used to hold the turrets
on the tube, or can be replaced with an extender to use single
objectives, and I have seen scopes built that way too. The only
exceptions I know of are Nikon and Olympus, and I've made a whole
bunch of adaptors for these scopes to use the Society standard
objectives. (If anyone can explain where "Society" comes from, it
might be interesting. What society?)

The Royal Microscopical Society. How's that for an obscure
and useless bit of information crowding out more useful
stuff from memory? Wish I could remember my wedding
anniversary.

Ned Simmons