You have a fairly special piece, a two tone Hamilton grade 940. The production on these was fairly low. What makes yours very special, though, is the condition of the two toning. Most of these are washed out, but yours looks to be fairly bright.
The dial on yours is in poor condition, however I wouldn't worry too much about this as it is an easy fix and well worth doing.
Whatever you do, DO NOT have the watch serviced, as any work of this sort has a significant chance of washing out the two toning and lowering the value dramatically.
I'd want to see the watch in-hand to give good value estimate. With the dial damage, I'd probably put the value at $800 on the low end, and would very likely raise it depending on just how good the watch looked in-hand.