Eagle,
An original box of Kynoch. You are correct about the moniker .242 Manton or .242 Rimless Nitro Express..
My Cogswell & Harrison Mauser is marked .242 Express.
However -
I suppose this comes as close to calling the cartridge a .242 Vickers as one can get?

Very much like calling the ".275 Rimless HV for Rigby Rifles" a .275 Rigby I guess?
Cheers, Mike