1953 Emerson 747
Coat pocket radio, thermoplastic cabinet (ABS)
6 1/8 x 3 ½ x 1 3/8 inches / 156 x 89 x 35 mm
Four subminiature tubes (1AG4, 1AH4, 1AJ5, 1V6), superheterodyne circuit
1.5v cell, 67.5 volt battery
Manufactured by Emerson Radio and Phonograph Corp., New York
This may have been the first large-production "pocket" radio. All other coat pocket subminiature tube radios appear to have been produced later than the 747, though at least two were brought out in 1954, maybe before the Regency TR-1: the Grundig Mini-Boy and the Silvertone 4212. It's also possible that the Koyo Parrot KR-4S1 came out in 1954, though as far as I know, no firm release date has been found for it.