Here is a Tannenbaum Beer Tap Knob from the Marathon City Brewing Company located in Marathon, WI.  This Tannenbaum Beer Tap Knob is from the early 1930s era and is in excellent condition considering how old it is.

This Beer Knob was made by the Harry Davies Company located in Chicago, IL; the style is known as a daka-ware ball tap knob.  This dakaware knob is made of a convex etched metal face mounted and nailed to a black bakelite ball body.  This particular style of beer ball tap knob is one of the earliest known types to exist.  These were produced shortly after the government mandated that all breweries had to have their own tap handles so they could be properly marked at bars and taverns when served.