That is a nice rifle but I believe it is a Martini Cadet; the Cadet was a small action, center fire Martini in .310 built for Cadets in Australia and are very popular as a platform for custom rifles.
The top is my wildcat 20 Raven - A rimmed and blown Vartarg
Middle - 17 AB
Bottom - 218 Bee
Enjoy your rifle, these little rifles are great fun to shoot. Some are put off because they don't have safeties, just keep the lever slightly pulled down until you are ready to shoot.
Don