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.