That's an interesting coin you have! I was able to find this reference to an auction sale back in 2012 of one in much better condition (AU-58): http://www.coinfactswiki.com/wiki/T...ler_Dav-8808
The fact that we can find more recent sales of 1591, 1593, 1594 and 1595 thalers but not yours may mean it is a more scarce type.
Yours is several grades lower (probably F to VF), but it also looks like it has a hole (or an attempt at a hole that did not go completely through)? A hole will significantly reduce the value compared to an unholed specimen, but if it is a scarce coin (which I suspect for yours), there will still be collectors with limited budgets who are interested in a holed example.
My guess is that an unholed specimen might fetch $500 or so in this condition, and that yours might find a buyer at $100-200. But the value of a coin with damage like that is very tough to guess accurately.