Unidentified Eley skin cartridge

I have not been able to attach a name to this cartridge. It appears to be a Tranter, based on the appearance of the bullet with its round nose and single deep groove, but the bullet is too large for a .450 Tranter and too small for a .500; did they make a .475? The diameter of the bullet is .472", and it is .550" long. The overall length of the cartridge is 1.055".