As to Campagnolo compatibility-
If original hubs, the area between the threads and the flange will be blank
one groove, English threading
two, French threading ( most often )
if later the hub will have the thread type marked
Regina freewheels- blank back side Italian, one groove, English or small F.1 French - two grooves OR a small rectangular punch press mark. Atom did the same for a time.
all part of the secret Vintage code.