DURING OCTOBER 1947 AS TO THE MARK "LONDON"; DURING OCTOBER 1946 AS TO THE WORDS"FULL FREQUENCY RANGE RECORDING," "FFRR," AND DESIGN.
DURING OCTOBER 1947 AS TO THE MARK "LONDON"; DURING OCTOBER 1946 AS TO THE WORDS"FULL FREQUENCY RANGE RECORDING," "FFRR," AND DESIGN.