[Collins] Winged versus Round Emblems

[ERogerWms at aol.com]

Hello: My only Collins radio is my cherished winged 51S-1, but I am 
considering a 75S-3C. I am confused by the relationshipship between the various emblems 
(ie, winged, small round, large round, Rockwell, etc) and age. My 
understanding is that winged units are older than round units, and, of course 75S-3B's 
are older than 3C's. Yet, there are winged 3C's and round 3B's. Were 3B's and 
3C's manufactured simulataneously for several years? 

I would appreciate any information on this matter, ie age and emblems. Please 
feel free to reply off-net directly to me.

Thanks, Roger KB4THL