Mc Murdo Key Morse key BCE type C307, same as BCE 502 made in England
This tiny key was used on many post II WW with British and Australian radios and portable field radio sets.
It was manufactured by "McMurdo Industries" in England.
It is completely sealed and waterproof and was also used on life rafts.The same style of key was used by the British Military in the 1950's, 1960's and 1970's.
The Australian army used a similar key, made by "AWA", from 1970 to 1995.
Non adjustable contacts which require about 283g pressure and have 3mm travel.