Quote Originally Posted by okto View Post
Leica's naming conventions actually tell you quite a lot once you know them, just like Canon's. Let's take a SUMMICRON-M 50mm f/2.0 for example. "Summ-" lets us know it's a double Gauss (aka Planar) design, "-cron" lets us know it's a mid-speed lens, and "-M" tells us it's got a fingertip focusing tab and the focal length engraved near the mount.
Leica.overgaard.dk seems to disagree with your definition. Summicron was derived from Leicas use of crown glass for the first time.
ALL Summicrons are f2 maximum aperture.
-M says it's an M mount lens not an R or reflex lens

Not all Summicrons have finger tabs, in fact MOST do not.