It was always my understanding that the Webley & Scott model copied by SKB was the post-WWII Model 700. The 700's have neither a rib extension nor an off-center top tang screw--nor did the guns made for Ithaca by SKB. My 1961 Shooter's Bible has a couple of pages on "SKB Custom Shotguns", and an add for an "SKB Royal Deluxe Shotgun". (The price for the basic Royal Deluxe, which was a double trigger, nonejector gun, is listed as $400--far higher than the guns later imported by Ithaca. However, the photos of those guns also show barrels with no rib extension, and without the off-center top tang screw.)