What is the value of Diamond Arms shotguns?

Sort of asking what a flat-head Ford is worth. I can guess that it is either a single or double barrel break action and in NRA Good condition. A single-shot would normally retail for about $50-$75 and a double $125-$150, but apparently .410's are getting popular with both shooters and collectors, so you may be able to double those prices.

Probably about $50-$75.