[bridkarl]

Found one of these for $30. Don’t have any radios it works on but it’s interesting.

[Brad Winder]

Well, now you need to buy a suitable set to match. 

[bridkarl]

After I move across the country it will be one of the first things I look for. Apparently this only works with large console sets -- which surprises me. I would have thought making it work with a smaller table size model would have been good marketing.
These links explain the operation and background of the device.

https://philcoradio.com/repairbench/myst...ration.htm
https://philcoradio.com/repairbench/mystery/history.htm

[GarySP]

That mystery control is in better condition than most I've seen. Usually the dials have warped over the years. This was a top of the line feature, and commanded a premium price. That is the reason it was teamed with top-end consoles. 1939 to 1941 various models had the feature until the war effort ceased radio production.
An interesting note gleaned from the Philco Radio Gallery, located at the bottom of the page, was that with this introduction Philco ceased development of high-fidelity receivers! Good luck on your search! Take care, - Gary

[bridkarl]

This has some warpage. Ron had an article about fixing that but I have not found it yet

[GarySP]

Also found in the Philco Radio Library! Take care, - Gary

https://philcoradio.com/library/index.ph...rol-dials/