This particular Leica M2 started out it's life in 1963 and was used by German press photographer Herbert Ahrens until his death. When I bought it the sticker from his 'Pressedienst' was on the bottom plate. It looked very beat up but was still working flawlessly.
The camera was stripped from its chrome in 2012 and repainted in semi-gloss black paint. The craftsman that did the job spent many hours tapping the dents out and he recoated the camera with seven coats of a special UK military paint. Every coat of paint had its own oven bake to toughen it and was subsequently sanded down a bit to make the next coat stick. Result: a very durable paint job. This camera is eight years older than I am and delivers the image every time.
A shot of re-painted Leica M2 with the then newly-aqcuired Summilux 35/1.4 pre-ASPH. Near-new, cool! It had been used for three rolls only, in 1982!
With the hood on, it's still a very small lens:
The trusty Leica M2 with my wide angle Super-Angulon 21/3.4 and the auxiliary viewfinder.
The Leica M2 with a Jupiter-9 85/2.0 LTM lens that left the factory in 1952 set to Leica specs.Elsewhere on this site you can read more about this remarkable lens and see pictures taken with it.
Checks to perform when buying an M2
Check if the rangefinder image lines up correctly.
Mount a lens and set distance to infinity, point the camera to a distant object and check wether the rangefinder lines up correct. If off horizontally or vertically, not to worry, this can be adjusted with the CLA.
Perform the same check for a closest focus image. Check if film transport is even by cocking and releasing the shutter a few times. Check all shutter speeds. Start with the slow ones, cock the shutter a few times and release. One second up till 1/15th second should be clearly distinct, slow gears (buzzing sound) should release evenly.
Remove the bottom plate and lens or body cap. Swing up the back door. Cock the shutter. Point the camera to a bright light source and look for any pin holes on the curtains. Release the shutter and check the second curtain as well!
Cock the shutter again and inspect it from the front, you should see no creases on the shutter but a smooth cloth. Do not touch it with your fingers. Release the shutter and inspect the second curtain.
Check if the take up spool is in the camera. I know, this sounds rather daft, but it's quite impossible (i.e. expensive!) to find one without a camera!
Check whether the frame counter advances. I have owned a camera on which it didn't, and its a PITA since you always need to carry a spare film and run out of film when you're busy or not expecting it.
Here is a nice video off YouTube to show what a Leica M2 looks, feels and sounds like!