Office of Steam Forum for Model & Toy Steam Gas & Hot Air Engines

I found this device at a local antique store today and was wondering if anyone here could help me identify it.  It appears to be homemade with copper wire wrapped around a wooden frame that is graduated in size.  There are two red and two black terminals on the other side as well as the white object that is shown on the front.  The brass arm rotates around the device and contacts the wires with a small brass ball.  There are two of these arms one on each side and they move independently of each other.  The copper wire goes through the wood and connects to  the terminals.  I didn’t buy it and I only have this one photo.  Any ideas?  Thanks for the help. Depending on what it is I may go back and get it.

Excellent! Thank you sir.

This is a crystal radio.  You can see the 'cat's whisker' detector with the gelena crystal on the bottom of the picture.  The coil of wire is the station tuner.

I also guessed crystal radio. That sure is a nice one .