This is the rimmed version of the 375 H&H Belted cartridge and was launched in 1912.
The CHAA headstamp is that of Custom Hunting, Ammo & Arms, Inc., of Howell, Michigan. The turned brass cases were evidently made on contract by Red Willow Tool & Armoury, Inc., Montana. Sold by CHAA as loaded ammunition under the brand name “SUPERIOR AMMUNITION.”
example of the Westley Richards Round Nose or copper LT CAP bullet