Well done Matt for being the first to get it right, and well done Brian for being a close second! It is, as you say, an example of the Arthur Hill 1933 patent pistol design.
I have to admit to cheating slightly, by giving the impression that it might have been an authentic example of the period – although I never actually said that. It is in fact a modern reproduction, a project I have been working on for a while which I have recently finished. I doubt that an authentic example exists as the gun was never commercialised, and Hill’s prototype has long been lost. So if it had been real, it would have been a very valuable find.

I have always been fascinated by old patented airgun designs that never made it into production and wondered how their novel design features might have performed in practice. The only real way to find answers to such questions is to make an example of the gun and test it - a sort of “experimental archaeology”, as they call it on Time Team, but applied to airguns. The Webley Whiting and the Webley/Frank Clarke twist grip pistols are two previous projects I have worked on and there are previous posts on these. The Hill pistol seemed a logical next project to take on. It is a two-stage cocking pistol, based on a unique system, and as it is more complicated than previous projects, I did wonder if I was biting off more than I could chew. But nothing ventured etc.

Arthur Henry Hill was a Birmingham based inventor and airgun enthusiast who is best known for the 1905 Hill and Williams air rifle, an extremely rare British air rifle, of which only about 200 were ever made. Hill also patented an air rifle design in his own name in 1908. He had some involvement with Webley, as a rearsight design that he patented was used extensively on the Webley Mark 2 Service air rifles. His 1933 patent for a unique two-stage cocking system for airguns showed its application to both an air rifle and an air pistol:









The pistol is a trigger guard/underlever cocking type, and is unique in having a floating muzzle plug instead of a the fixed plug found in all other airguns. So when the gun is cocked the muzzle plug moves out of the cylinder as the spring is compressed but is held in place by a roller wheel attached to it which rides in a grooved extension to the cocking lever. When the cocking lever is at right angles to the cylinder the sear engages with the piston and locks it in place, and at this stage the spring is about two thirds compressed. When the cocking lever is pushed back home, the muzzle plug is forced back into the cylinder and compresses the spring by the final one third. The trigger guard is locked in place by a spring-loaded catch in the grip.





The general idea is that the two-stage compression of the spring requires a lot less effort than a single stage compression and so makes the gun easier to use.
Now having made the gun I have been putting it through its paces and I will be posting my conclusions soon.
If there is any interest in how I made the gun, let me know and I will be happy to put together an illustrated account of the project and how the gun was made in a separate post.