I'd second Vail's suggestion that this was a Martini brought to the US and rebarreled at some point after importation. I've owned quite a number of small frame Martinis, only one of which was in the original centerfire caliber (.310 Cadet) and a couple in the original .22 long rifle. Several of them had take-off barrels from American manufacturers, reworked to allow them to be fitted to the Martini action.
There was never any doubt that this was an English reciever with a US barrel installed. I was wondering if it was possible Stevens did it. After the comments and some further research, I am convinced they didn't.
The thing to note about this rifle is that it is not a Cadet. It is a small frame Martini which is a distinctly different animal and were sold as commercial rifles built to a different standard than the military actions. They predate the Cadet by a couple of decades. They were scaled down from full size Martini actions and were fitted with safeties. They had a normally assembled action, and did not have a drop out trigger group. They were made by several makers, and some manufacturers (such as Tranter) made them for the trade. Dependng on their size they were used for rook rifles up through medium bore sporting rifles. They are much less common than the Cadet by an order of magnitude, and not many were available in this country during the period. The US had more single shot rifles and manufacturers than anyone at that time, which caused me to be really surprised at seeing the gun with a US barrel.
