Inspect those used revolvers carefully.

[browningautorifle]

There are hash marks on the inside edge of the side plate showing him someone has been doing something with no knowledge of how to go about it. The thumb test is cock the revolver and try to push the hammer off the trigger...here's a list of things to consider...

http://www.chuckhawks.com/used_handgun.htm

I have an older mod 18 that I take to the range to finish up with. Strange after shooting everything else, it comforts you that you can still do golf balls at odd ranges.