Group of four spark/maritime keys, from left to right:

U.S. Navy flameproof key marked “CMI- 26003A”.

Manufactured by the Moulded Insulator Co.

Spark key made by the Signal Electric Mfg. Co. Diameter of contacts: 1/4 “.

Also known as the “Standard Wireless Key”.

Spark key marked “Mesco” (Manhattan Electrical Supply Co.). Diameter of contacts: 1/4 “.

Key with 3/16 “ diameter contacts.

Underside of knob is marked “Dyna”, of French origin.