Group of five keys:

At the back a J-37 key attached to a large clamp.

The key swings for proper use while the clamp is  held at the operator´s thigh.

Front row, from left to right:

Flameproof key J-5-A made by the L.S. Brach Mfg. of Newark, N.J. for the Signal Corps, U.S. Army.

Key type 502 manufactured by BCC, of London.

WT 8 AMP key No. 2 MK II marked underneath “ZA 16929”.

Another variation of the WT 8 AMP, manufactured by Westclox, Canada.