I am growing a little tired of my Fed3 because of the dim and small viewfinder. So I have found a couple of M2's and M4's that are on sale in Stockholm right now. They sell for around 4000 - 5000 SEK (615 - 770 USD). I'd need a lens too of course.

The features seem to be comparable. Mechanical shutters and large viewfinders. I already held the M2 in my hand and it felt good. And now comes my question: what should I look for when checking them out? Shutter fired beautifully on the M2 specimen that I held, no lens attached though.

Expose a test film for shutter checking, I guess. Clean view- and rangefinder glass? How can one know that it has been properly kept?

For a start I will most probably attach a russian Industar 61 (which is screwmounted, so I need an adapter). I'll buy a Leica lens a bit later.

Thanks in ahead for your excellent advice. I really mean it.