As jimmy found, proofmarks are British, but I could google nothing on W.R. Bush. He may have been a small maker or more likely a distributor or even dealer who had commodity guns marked with his name.
Yours not only lacks the foreend and foreeend iron, the retaining lug has been pulled out of the bottom rib; apparently after an old solder repair from the first time it broke off. Resale value is nil unless somebody needed a set of back action locks.