This nice Marconi Type 100 or is it a 100A? Morse key is a great smaller key to use. With two connections at the rear for wires to the radio transmitter. There appears to be pins on each side edge of the bakelite for sliding on a cover. Here is a recent photo of a Marconi Type 365B in the rear with a Marconi 365C in the front. One coil is removed from the front area of the 365C and the Lever of the key is an original 365A lever. Also the terminal blocks were missing on this key so I made my own attempt at 3 brass terminals with M4x70 by 10 cheese head slotted screws for the wire securing. Not professional at all with a drill, tap, and hacksaw, HI... It is acrually a very nice working Morse key. The black bakelite shroud usually over the front end of the key's lever was missing. I took some black heat shrink to cover that somewhat for a partial original look. More amateur work, HI.