The so called 'horseshoe' top lever was a feature of the P Webley 'Screw Grip' patent and was used extensively on guns supplied to the whole British guntrade, either in the white, fully finished or anything in between.
The only gunmaker's name I have never seen on a 'Horseshoe' Webley is Purdey and that is probably because I haven't looked hard enough!
The 'Horseshoe' is a piece of metal, shaped as per its name, that surrounds the forward end of the fairy normal looking toplever.
It forms the normally visible part of the 'Screw Grip', a method of griping the top surface of a simple top rib extension by use of a threaded toplever shaft turning in a threaded breech block. As the toplever is pushed to the right it rises in the breech so releasing the top extension by virtue of a slot cut in the underside of the horseshoe and, likewise, as the toplever return to the centre position with the barrels closed, it cams down on the top extension to add the 'third bite'.
None of the guns in ellenbr's post are very clear. Hopefully the one below is better.
The gun is a 16b P Webley that I sold a couple of years back.
The part engraved 'WEBLEY PATENT' is the 'Horseshoe' and is separate from the toplever that it surrounds. A common feature is the secondary locking pin.
Interestingly, the 'Horseshoe' toplever was even used when there was no top extension used which just underlines the high regard that Webley's trade actions were held in by the British gun trade.
