Very nice Rubicon Company Potentiometer probably from 1930s.  Last inspection is from 1970.   The brass armatures slide over the brass tabs to adjust voltage.  This is an untested piece.  Comes in it's own wood box.  Some wear to box.  I don't think the latch is original.  Great conversation piece.  You will love showing off this piece!

While you are here please look at my other listings.

Thanks!