Of course flat faced cocks belong with flat faced locks, etc and so sometimes it's easy to see something is wrong, like when a round-faced cock is on a flat faced lock or vice versa. I think it takes a lot of exposure to begin to appreciate the different models available from different sources over al ong period of time. Lots for me to learn.
I think when most people say, "German locks" and "English locks" they really mean "German locks found on American arms" and "English locks found on American Arms". As Chris and maybe others mentioned there are plenty of round-faced Germanic locks found on European arms but they rarely have been employed on scratch-built guns here. It looks like French locks were sometimes used in new England and for sure Dutch locks in the Hudson Valley of New York. The Dutch locks look like early English locks to me, which makes sense since the English used a lot of Dutch arms from time to time. The Dutch were avid arms dealers.
The Germanic export locks as represented by commerical offerings you can find in catalogues now include the Davis jaeger lock we've had available here since the late 1970's (very early banana styling, probably 1680-1720), the Siler (probably represents a 1770's-1780's export lock), the Jack Haugh early lock w/o bridle (often gussied to sell as a Tulle, etc and probably mid-1700's styling), and now the Davis early lock, which is probably third quarter of the 18th century in styling. All these are flat-plated locks with faceted pans, etc. and it seems that was the case for nearly all Germanic export locks used here. More confusion is based on the absence of a pan bridle. Once thought to represent earlier locks or cheaper locks, we now know that is not accurate. Size of Gemanic flat-faced export locks and curvature of the lockplate do seem to diminish more or less progressively from 1700-1800.
Earliest "dog" locks from England were flat faced (here I mean locks with a safety dog hooking the cock) but after that very early period, English export locks were often round-faced. However early Ketlands and others were flat faced. Pans are round whether the lock is round or flat-faced. English export locks are represented by the Chambers English Round Face and Queen Anne (mid 18th century), the R.E. Davis round-face fowler lock (a nice typical export quality lock fof mid 18th century styling) the flat-faced Ketland locks by Chambers and others (produced over a long time frame), the flat faced Twigg, the flat-faced but beveled L&R Durs Egg (1780's), and finally the L&R Ashmore, Manton, etc. (late flint) among others.
In general later English locks had a pronounced S-curved cock (see the L&R Durs Egg) with a less full "breast" than the Germanic locks.
Lots more could be said and I made some gross generalizations. We haven't even touched French or Liege designs.
