What about here? Is that not a Webley? It looks break top.
"By 1938, Jones carried a commercially-available British Webley "WG" Army Model .455 caliber revolver during his trip to find his missing father and recover the Holy Grail. (Note: While some written accounts indicate the model to be a Webley Mark VI, recent research and DVD screen captures prove that the 'screen used' pistol was the "WG" Army.)"
You are correct that he did use a S&W, I stand corrected.
"His weapon of choice was a large Smith and Wesson Revolver ('N' frame type) with a shortened barrel. In Raiders of the Lost Ark Jones packs a .45 caliber S&W M1917, for the trip to Peru, which he ends up surrendering to Belloq; then in Cairo he uses a S&W 'Hand Ejector, Second Model' (also referred to as the 'Hand Ejector 2' or 'HE2') to dispatch the menacing Arab Swordsman."