The ding, if minor shouldn't cost more than $50-60. Back on face might be a deal breaker, it depends on what needs to be done, but $400 is a good price. 6/31 is June 1931. What length are the chambers? If they're 2-3/4" the gun should be stamped 70mm. No stamp they should be 2-1/2"
I have similar small framed 16, weighs around 5-10. Nice little guns.
It all depends on the reason it's loose, perhaps all it needs is a good cleaning. But at that price, if the barrels are sound and the wood is too I'd go for it. Probably game scene engraved?
