Condition is more important then chrome or black.
Take the bottom plate off, open the back door and put your eye to the back as you check out each shutter speed. For 1/60 or less, you should see a circle image from the lens since the shutter is wide open at these speeds. for faster speeds, you should get a glimse of light, its a rough method of shutter verification. If possible, run a roll of color reversal film and have processed somewhere fast to verify no light leaks etc.
The newer the lens the better in my mind to avoid age problems and a newer 50mm summicron is a great lens. Of course I still have a 1964 DR Summicron that is in excellent condition but some are not. Good luck.
BTW, you are taking the right approach by being cautious, doing your homework and not jumping at the first thing available.-Dick