Your Midland gun needs more info to value accurately, but.....
It is a competent but modest Birmingham boxlock, extractor, proofed for modern smokeless 2 3/4 12 gauge shotshells with 1 1/4 oz of shot. The 13 1 marking indicates a tight dimension for 12 gauge bore.
Close examination of the barrels is required to know more. Whether the bores are clean and smooth, whether the bores have been lapped or worn in their lifetime to be out of proof.
Measurement of the chokes with a micrometer would tell one whether it has a desirable configuration. Overall weight of the gun, drop at comb, drop at heel, length of pull dimensions should be listed to help ready a gun like this for sale.
External appearances show the gun in good enough condition to be worth some investment.
One man's opinion - in repaired, fully functional condition value would be about $1200, $1500 on a really good day with the wind blowing your way. The way it is now, perhaps $800.
If you have to pay a high end gunsmith to repair this gun you might have more in it than its ultimate value.