[Leica] 50/2?

[Byron Rakitzis <byron@rakitzis.com>]

OK, I've decided to get a 50/2 for my M6, and I was hoping someone here
could help me navigate the morass of used lens listings: there are so
many things called "summicron" that I'm unsure how to find the thing
I'm looking for without seeing it in front of me.

Specifically, I'm looking for a lens which will take the round clip-on
lens hood which some ads list as "vented".

As far as I can tell this is the generation of 50/2 immediately previous
to the current one.

What I'm wondering is what to call this lens? "Summicron-M" isn't specific
enough, is it? Because I thought that referred to the lens I'm looking
for and also the current version.

Another question I have is: does it matter whether the lens was made in
Canada or Germany? I am not trying to get into a religious war about
Canadian vs. German craftmanship, rather wondering if either or both
lens types can be fitted with a clip-on hood.

Perhaps the best thing I can do is call a reputable dealer who understands
all these nuances and can sell me the right thing. Keeble & Shuchat in
Palo Alto doesn't have one of these lenses on their shelf right now,
and they were my first choice since I could be there in person.  KEH in
Atlanta would be a bad choice, I think, because their sales staff is
very hit or miss: they often only know how to read back to you what's
on their computer screen. I've heard a couple of recommendations for
Don Chatterton. Is there anyone else I should be calling as well?

Many thanks,

Byron.