305 and 355 G-Claron into shutter?

[Brian Bullen]

I've read on this forum that some of the older 355 G-Clarons won't fit directly into a Copal 3, is there some way to tell by serial number which ones will go directly into shutter. Also does the 305 go right into a Copal 1 or is it the same deal as the 355, older ones may not. Thanks for the help