Here is a Yuengling Cooler Knob from the Yuengling Brewery located in Pottsville, PA. This Yuengling Cooler Tap Knob is from the 1940’s era and is in excellent condition for it’s age.
Knobs like this Yuengling Cooler Knob were used to replace the round handles of large bar back chest coolers. They would serve as a marker to which cooler door had what kind of beer and from what brewery as well as advertise Yuengling Beer to patrons sitting at the bar. The way you can tell ball tap knobs from cooler knobs is by the shank hole. If the shank is threaded then it’s a ball tap but if it’s square-shaped then it’s a cooler knob.