Hallmarks go back to the 1300's. Many countries have their own system and hallmarks. The legal requirement for US to hallmark did not exist until 1906. I could not find your hallmarks, probably it is not British, try researching from the third link below.
I am not sure which is right-side up, the close-ups of Hallmarks may help others in IDing them.
Looks like the ring is hallow or folded over in its making.