One of several British developments during the early years of the 20th century when the British banned all .450″ rifles in Africa and India.
Proprietary loads for Cogswell & Harrison. The latter specimen does not have the “·475 E” in the headstamp. There is no mention of this headstamp in Fleming
The first specimen is a proprietary load for a South African client by OPM. Still trying to find out who he is.