It most certainly was Lancaster!
There were quite a few .22 calibre ones (including full length versions), 6mm or .243/303, .25/303. the . 270/303 which you have there. These were all the rage up until the late 60's or early 70's when imports from England (Parker Hale, BSA etc) & America (Winchester, Remington etc) became very popular & these literally just disappeared. I have heard of a .35/303 & even a .375/303, but can't recall seeing these calibres back when I was a young fella!
From memory Super & Riverbrand Cartridge Companies used to make loaded rounds.
You have a fairly rare bird there mate, I haven't seen or heard of anyone having or reloading one in years!