English Nitro Proof marks which put it between 1896 and 1904 as that is when they used the word Maximum after the weight of shot. Looks like it was made by W.C.Scott judging by the action. Possibly their Model 169. As to value a lot will depend on whether it is an ejector or non-ejector and if it is still in proof. I live in England and the value here will be a lot different to the value in America. If non-ejector say £200 to £300 and if ejector say £600 to £800 if still tight and in proof with no pitting. Best to take it to a nearby and reputable gunshop. Sale value will of course be different to insurance value. Lagopus.....
