Hello Richard:

I think the Cardwell company was owned by another company, which was owned
by the Cardwell family. At some point, during the demise of Hammarlund,
that company purchased the Hammarlund assets.

The specified audio output of the Cardwell receivers is high enough that it
was probably push-pull. So, if you ever find one, the audio will probably
be good.

I just had a thought about searching for this elusive receiver. Check the
various manual sources. If there were a few radios made, there must have
been a manual floating around. Fun to see one.

73, Colin K7FM