Fungus the camera killer; checking for fungus is a good place to start, it shows how well the camera has been stored and cared for.
Remove the lens look through it, does it have a frosty spider web appearance? Fungus on the lens isn't the end of the world, but the cleaner the lens the clearer the images.
Fungus can wreak havoc on your camera collection, remember fungus is alive and can continue to grow and spread in the right conditions. UV light will kill it, stopping it from spreading, but ultimately cleaning it off is what you'll need to do.
If you plan on having it cleaned, you will want to asses if the fungus has started to etch its way through the multi coating or even into the glass, once its at that stage, there's no going back.
2. Battery acid
Battery acid; another camera killer.
Always remove the batteries from you camera when storing for long periods of time!
Battery acid can leak right through the camera then crystallise, completely destroying any electric components. If its still in liquid form it maybe savable, but keep in mind that it may cause issues down the track. The acid etches away at the metal, causing battery contact issues.
3. Light Meter
Put some batteries in, does the light meter work? When you point it at the light does it change? You might need to half press the shutter button to activate this. Test it against an external light meter, how far off is it?
In automatic or semi-auto cameras this can be a big issue; if the camera is relying on the meter and the meter is out, your exposures will be too.
4. Film Winding
So, the lens looks good, the batteries are in, but does it advance the film? Open the back, watch it turn as you advance it.
In an ideal situation you will want to put a blank test film in, close the door, wind and check its advancing and doesn't rip or tear the sprockets. Some cameras may pull the film and push the sprockets, if these are out of sync the sprockets will tear.
5. Shutter Jam
Does the shutter fire? After advancing the film, press the shutter. If it doesn't fire, check that its not in a lock position (often indicated by an L). It could also be switched off, some camera will not fire when they're off.
A common issue with 1960-70's range finders can be the timer, give the timer a push.
6. Slow Shutter
So it winds, then fires, but is it actually changing the shutter speed?
Open the back, change it to 60th of a second. Fire it 3-4 times, look and listen, does it appears to open and close at the same rate each time? Turn the shutter dial to 1 second, does the shutter open and close for 1 second? If it's not consistently firing at the correct speed, it could be lagging or sticking.
7. Auto focus or jammed/sticky lens
If the camera has an auto focus lens, look through the view-finder and half press, is it in focus? Turn the focus wheel on the lens, is it stiff? Turn the aperture wheel, does it turn? Does the lens feel smooth with no sticking?
8. Stuck Aperture
Another common issue, especially if the lens has fungus. Look through the lens, close up the aperture and fire the shutter, did the aperture change size? If the camera has an aperture preview next to the lens, press it, and change through the aperture settings, does the aperture open and close or does it stick?
This is very important on the fixed lens range finder, as you will be 'stuck' with this one lens!
9. Light Seals
Light seals are another great indication on the overall condition. Check along the back door, are the seals sticky? Light seals are often made from rubber foam and over time it breaks down. They are a bit of a mess to clean up, but relatively easy to replace yourself.
Light seals are another issue that you can only fully be sure are in good condition if the camera has been film tested.
10. Shutter Dampener
Take the lens off, the shutter dampener is there to stop shutter slap. Touch the dampener with the back of you nail, does it flake or crumble off? The shutter dampener is made from open cell rubber foam and over time it will crumble away, leaving black bits all through your camera. This can be a real pain in the view-finder!
Never touch the shutter damper while the camera is upside down, this will result in it flaking off directly into the view-finder!
While you have the lens off, check if the contact mirror clean and clear, avoid touching it, they can scratch very easy.
So the camera looks good? Make sure you understand and accept the sellers' returns policy.
Will they accept it back if you find a fault?