Here are 2 British Nitro Express cases I acquired earlier:
What are the correct calibre (case length) designations?
The first one is .500 calibre and has an OAL of 2.375in. Headstamp is “C KYNOCH C .500”
The second one is .400 calibre and has an OAL of 2.37in. Headstamp is “KYNOCH .450-400”
The answer to this is probably simple.