If it won't fire....the only reason to buy it - is for parts. Value might be $50...
But a break open ...single shot shotgun...has very little appeal in the market.../ you can buy a number of pump guns on the market, new, for under $ 200.../ and some really nice pump guns, even in a 28ga, for $ 500 - $ 600.
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But the only reason I'd buy it for parts ...is if I had another identical model - and it needed some parts for repair ..../ a gun like this, that won't fire on top of it, has no value to me.