Concentric barrelled pistols have always interested me, not too sure exactly why but maybe it's because they are so different from the more commonly encountered over lever or break barrel designs that you see more frequently. Undoubtedly there are design issues with them that have been resolved in various ways throughout their evolution & some were better than others but this example is very interesting as it shows both a good understanding of the issues that the design inherrantly has ss well as demonstrating well engineered solutions. As to who might have made it, well I can only think of those already mentioned like Clarke, AABrown etc but with a possible dating ti the inter war years I'd like to think it might have been a design BSA were contemplating putting into production at some point. There again it looks a bit Ackvoke'ish, albeit a well engineered one, maybe a for runner of it that was altered a fair bit for post war production with the materials shortages / tooling shortages. It will be interesting to hear who it might be attributable to.
Still strikes me as odd that BSA never put an air pistol into production until so late on.