Thanks, although the online source seems to give info only on Emil and later models. Quite little is to be found about the early Messers B/C/D. This book is perhaps the best and seems to have reasonable price too:
http://www.amazon.de/Messerschmitt-1.../dp/3844865977
When it comes to armament, I remember to have seen one C-3 with a pair of 20 mm wing cannons in Polish book on Bf 109 C/D in September 1939.
Most Bf 109 B/C/D in Spain flew without radio equipment - if I remember correctly Günther Lützow ordered radio masts and antenna wires to be removed as they slowed the speed and the equipment was not yet reliable. Also photos and colourplates of Mölders Bf 109 D show a plane without radio mast and antenna wires. At some point the radios were fitted again as they were useful to keep more loose formations together. But it took until Emil that the radio equipment finally became standard in Legion Condor Bf 109´s.
When it comes to Bf 109 it is not difficult to find info when it comes to E and later models (there is abundance of information). But when it comes to B - D, it is another story.
Was Bf 109 a superfighter already when it was B/C/D? I have read that Günther Lützow made same mock-fights against Fiat CR 32. He noted that Bf 109 B and Fiat CR 32 climbed equally up to 3000 m but above that altitude the biplane climbed faster! In turning fight (Kurvenkampf) the biplane was better, but not as much as he had expected.
It would be interesting to compare Bf 109 B/C/D with I-16 (tip 5 and 10) to see differences in speeds at different altitudes, rate of climb, dive and manouverability.