[Boatanchors] Harrington GP-20L

[Ron.K3PID]

I am trying to track down information on a commercial grid tuning assembly referenced in a 1965 handbook as Harrington Electronics GP-20L. All of the big deal search engines come up empty handed as does the ARRL archives search engine . Any chance a member of this group knows of or has information about this unit. It apparently has two windings with multiple taps and includes a band switch for the 5 ham bands.

Regards as always
Ron K3PID