Members are answering, but what are they answering about??
The (I) - 1959 - or the (II) - 1990.
I got my (II) 'as new' for four-hundred fifty Euros, in 2006.
Cheap and interesting. Not a "wow!" signature as in the 24/2.8 ASPH and 35/2 ASPH (or the 21/3.8 SA or 35 pre-ASPH Summilux in 'old-look' terms), but one that approaches these and is far superior to that of the wishy-washy, generic and ultimately uneventful 50/2 (IV)'s.
That's if you are interested in the fingerprint.