Current indicates that it is the version with a collapsible hood and no focussing tab! The formula is the same as the version made between 1980 and until the collapsible hood version came out (1999?). The earlier version requires a sep. hood, but it does have a focussing tab (something that I deem essential with 50 and shorter lenses). The collapsible hood on the current version is not that good! It keeps collapsing at inopportune times and if you carry more than one body and shoulder bag cameras - there is a fair chance that you will scratch the front element. I had one of these and modified it - drilled a couple of holes in the barrel and put in a focussing tab and also drilled a hole in the hood and used a setscrew to hold it in extended position permanently.
The later Summicrons are good performers - not as good as the Zeiss Planar 50/2, but close enough. The major weakness is the plastic "driver" for the aperture blades. These can crack or split and scramble the blades. It does not happen often (in my case twice with two different lenses, both heavily used).
The later 50f2 is also resistant to fungus and fogging. The earlier ones you have to check carefully for this.
I strongly suspect that Leica will be announcing a new Summicron 50 next year. It is now the only lens in their line-up that has not been "upgraded" and it is an old design and it has probably been tweaked and masseged to what can be done without going for a radical new design. Unfortunately, a new Summicron 50 will probably be considerably more expensive than the current version and also more expensive than the new Summitar 50f2.5.
