The first ones have a metal dial with painted numerals and a blue steel pointer. Later ones have a transparent plastic dial with imprinted numerals, and the pointer is beneath it on a painted metal disc.
Ben Bolt Painted Metal Alarm Dial
Alarm Dial Metal:
Metal dial with painted numerals and a blue steel pointer. Used through late 1935 or early 1936.
Ben Bolt Plastic Alarm Dial
Alarm Dial Plastic:
Transparent plastic dial with imprinted numerals, and the pointer is beneath it on a painted metal disc. Used starting late 1935 or early 1936.
