Sounds like you came across one of the older guns. I wouldn't buy it without seeing how it shoots first. At best it may be worth about $250, at least I wouldn't pay more then that.
Charter Arms has a good reputation for reliability. They are solid little revolvers.
But you have to realize, they are low rent guns to begin with. It didn't cost more than $250 new, and it wouldn't cost any more than that to replace. ANY used gun is going to take a hit in resale value. $200 is a fair asking price for a used Charter Arms in my opinion.
Basically, you wont get enough money out of it to justify selling it. Its a solid little gun, but its just not worth much money on the open market. keep it for your own use, and enjoy shooting it.
Keep it, is my advice. BTW, does it have an ejector shroud? If it does not, for sure one of the older guns, and more reliable than the newer production.
I say pounce on it. I have an older one (pre Charter 2000) that has been through the mill and still has pretty good lock up and a real good trigger. I really like it.