Three military keys, from left to right:

Key Telegraph Manual R.O.F. Blackburn.

Used in the British Army “Clansman” H.F. transceivers.

Telegraph key marked “Unit Operator No. 1 MK II, YA 8414”.

Key marked “MK 2   320-99-949-11 74”.

It has the British Army arrow, believed to be used with C11, C12 and C13 portable field radio sets.