My thoughts don't really matter, yours do.
But here goes.
If it was me, I wouldn't even consider dealing with this revolver.
You assume a lot about the condition of the piece.
If it looks well used, it probably is, and if it looks like it needs a good cleaning now, when it is up for sale, chances are that it has needed a good cleaning for a long time.
If they don't care enough to make it look decent to sell, how do you think it was cared for for many years!
If it is a gun you are going to throw in your tackle box, or tool box, maybe.
But even then, there is no excuse for not taking care of it.
You know they are not going to drop to a price you feel is acceptable, so why waste your time dealing with it?
Seems to me you have done your homework, in looking up completed auctions etc.
Use the info you have learned, and make a decision.
MY best advise?
Spend the money, buy the NIB 686 that is listed on GB right now, and have a QUALITY piece in New condition, that will be very nice, reliable, and last the rest of your life.
This one stands a good chance of being a piece constantly in need of parts/ work, and at the end of the day, you still have a $ 100 gun.
Another large consideration is the missing 22 lr cylinder.
Sounds as if this is going to be a plinker. I personally am a huge 22 mag fan, but I don't shoot much at all anymore.
Mag ammo is very expensive, if you are just going out to kill pop cans!
There is no reason you can't shoot and enjoy a NIB piece, it will maintain it's value well, if you take care of it.
Buy it, shoot it, enjoy it, and at the end of the day, when you clean the revolver, you will have a piece you are proud to own!!
You will be better off in the end.
Jim