Circa 1972, there was an ad in "73" for some new Signal Ones. A
receiver, and maybe a transmitter. My guess was it was the big fat
November issue that year, if anyone has there issues in better state
than mine. I suspect they never went beyond those ads, though.

I figured a CX-5 might have been one of those, except that I saw
no reference to such equipment beyond that ad.

Nope, was initially designed as an integrated station (1969), receiver
(dual) and tracking transmitter. Actually, the designation was :
CX for "Century series"
-7 for 10^7 Hz, ie 30 MHz. (Initially thought of including 6 meters, but
that was dropped before the first one was built. Almost made it a CX-8.

The 11 was a different manufacturer, never did understand the rational of
that other than it sounded good.

W4ZCB