My Lorch-Schmidt lathe uses 12.5mm collets and I have a few missing from the set -- I'm tentatively trying and find out how standard these are as an item. After asking around at Alexandra Palace juding from the blank looks most people seem to think I've got the dimensions wrong! From my initial perusal of some catalogues they aren't standard at all -- Schaublin seem to use 12mm as their standard.
The set I have are partially Lorch and some Crawford (CC).
Alan Bain