Note
QST, Feb 1948, p. 99.
QST, Jan 1949, p. 123.
>>> QST, Dec 1955, p. 181. (Harrison Radio listed near the Vibroplex ad) <<<
>>> QST, Jan 1956, p. 123. (Henry Radio) <<<
>>> QST, Mar 1956, p 132. (Harrison Radio) <<<
There was no mention of Mon Key between 1950 and 1955.
The first commercially available electronic keyer.