Pocket-Size Wire Recorder (Aug, 1953)

Seems like you’d need a pretty big pocket if that hand holding it is any indication

Pocket-Size Wire Recorder
PERHAPS one of the most sensational units to appear on the wire-recorder scene recently is a complete battery-operated recorder, 6-3/4x 4-3/8 x l-1/2 in. in size. It records, erases and plays back through a pair of lightweight earphones.

The entire recorder fits any average-size pocket, or it can be carried and operated in a fabric shoulder-type carrying case, as illustrated in photo A. Two types of sensitive miniature crystal microphones are available, as shown in photo D. One is a lapel variety and the other is a wrist-watch type worn by the operator in photo A, for making concealed recordings useful in detective work and for checking comments in crowds at shows and similar applications.

This Minifon recorder, made in Germany, is now available on the American market; it is powered with standard miniature A and B-batteries. The motor is driven by a Mallory mercury-cell-type battery pack that sells for $4.25. This provides 24-hour service. The A and B-batteries last for full shelf life. An a.c. power-supply unit also is available for operating the motor from 110-120 volt a.c. lines. Photos B and C are internal and external views of the recording and playback unit. Recording wire is available in spools providing 1/4 to 2-1/2 hours of continuous operation.