Victor VV-XVI L-Door

[estott]

Pacent was a maker of electric pickups (the Phonovox line) including some that slipped onto the tone arm and plugged into your radio. Would have looked something like this:

[gregbogantz]

That Pacent article appears to be the connection adapter that allows the electric pickup to be connected to the radio. This was for radios that did not have a specific phono input connection. It looks like it was designed to fit under the typical 5-pin #27 detector tube which was commonly used in radios of the 1929 period and for a few years thereafter. The adapter fits around the pins of the tube, then the tube is put into the radio socket. Connection is made between the grid and the cathode of the tube which would function as an audio amplifier in this connection.