Elmar M 1st is an M mount version of the original 50/2.8 LTM Elmar, with the aperture iris right behind the first lens and with almost circular aperture. It is lower contrast, and somewhat soft wide open, sharpens up around f 5.6-8. The second version has been made in the nineties, I believe as part of some special edition Leica, and then it has remained in production for a few years. The lens has been recomputed, the aperture is now more recessed and it only has 6, although somewhat curved blades. One minor improvement is that the f stop ring does not rotate when you focus - I believe Tom Abrahamsson was actually responsible for that ;-). The good news though, is that the lens is substantially sharper and very flare resistant, while conserving a Tessar like 3D effect and very pleasant bokeh. Mr Puts claims it is almost at par with the later Summicron versions, perhaps even sharper in the field. The rendering in B&W is particularly equilibrated, with medium contrast.