Just for info, one of my Seniors, that I am sure was getting on to the last made, knurled barrel (1939-40?) serial number S18539, black grips (yes, they did do some) without 'Webley' logo. Patent details on RHS chamber, no Birmingham 4, just Birmingham, small P at the front of the trigger area.
If you had a post war Senior and wanted to make it look like prewar just add some number to the batch number stamped on the front. Anyone looked under the grips?
My personal opinion would be fraud, no Seniors had 6 digit numbers, could be an apprentice at Webley playing games(?).
lodmoor
Always ready to buy another Webley pistol and another and . . . .