It's Webley's "Proprietary" Hammerless Ejector Model, Grade 1. There is an illustration of this same gun in Webley's 1922 catalogue. Serial number in the 97,000 range would indicate a date of roughly 1923. The proof marks are 1904 rule Birmingham, which fits. However, I don't see the crossed sword date code mark that Brum started in 1921. That would give the date of proof. Nice gun.

"Serious rifles have two barrels, everything else just burns gunpowder."