Four keys of British origin.

The brass plate of the one at the right says: “Supplied by WILTON & CO. Electrical Engineers BEDFORD”.

At the center, front, possible hand made.

The one at the left  makes signaling contact with the screw on top, which also acts as gap adjustment.

The one at the back has a condenser inside the base (no value shown) connected across the working contacts, marked “Mansbridge Type Lissen Condenser”.