You guys are correct, the photo of the internal side of the lock is from a flat faced German lock I considered making. But, considering how long it is taking to do the round faced one, I don't think I will live long enough to do the second one.
As far as old guys skiing, I once overheard a French ski instructor tell his student who was not satisfied with his technique, "What do you expect, you're been skiing only 23 years." I've been at it much longer than that and (hopefully) have improved over the years. At least I very seldom fall. Actually, at my age I'm too darn afraid to fall. Something would surely break.