Philip Webley & Son (Webley & Scott after 1897) invented and built several patterns of double gun "screw grip" actions, both boxlock and sidelock. The two you mentioned were boxlocks primarily used as dedicated double rifle actions. The correct name for the action with the spade shaped rib extension in the photo above is the A. & W. C. "A" for the Anson & Deeley boxlock patent of 1875 and "W" for the Webley and Brain screw grip top fastener patent of 1882. The "C" is said to be for Cordite and is used to differentiate it from the A & W shotgun. The PHV-1 is substantially similar and was, with respect to Webley retailed guns, intended as a plainer grade model, but some of those built for the trade ended up anything but plain. There is very little difference between the two and both are techically screw-grips.

Webley retailed some of these themselves, but most were made "for the trade" (built for other gunmakers who retailed them). While Webley did sell these to the trade as actions only, most were more complete than that when they left the factory. Webley assigned and stamped serial numbers to these only if they barreled them, the numbers being stamped on the short-rib (early) or the left side of the fore-end loop (later, this began with no. 13000 which, as nearly as I can tell, was around 1909). If you think you recognize the action, remove the fore-end and look for the number.

In my database, I have boxlock double rifles built on these two actions, with Webley serial numbers on them (which means that they left Webley, at a minimum, as proven barreled actions "in the white"), from Wm Evans, Rigby, Holland & Holland, Army & Navy, Charles Lancaster, George Gibbs, Joseph Lang, Churchill, London Sporting Park, Manton etc. (by no means an exhaustive list). They're fairly ubiquitous. Some retailers "bought in" these "in the white" and stocked/finished them themselves (I recently researched a Lang that was) but most were probably bought in complete.

The screw grip top fastener is what makes these special. I have a strong preference for a rib extension on double rifles, but don't like third fasteners unless they're screw grips.

Some "screw grips" are inert, meaning that the lever must be manually closed, such as the Jones patent underlever action (although Purdey built some of these as snap actions) and the Wilkinson Sword Co patent screw grip fore-end fastener (which is the one used on most of the Webley screw grip double rifles). However, both of these actions are snap actions, meaning that a spring rotates the top lever closed when the gun is closed.
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