It seems that baseball bat mufflers first appeared sometime in later 1960 or sometime in early 1961. Prior to that Ludwig was using a small knob as the primary muffler adjustment. Around March/April of 1968, Ludwig switched to a large round knob as the primary muffler adjustment. Years ago I used to think the Ludwig phased out the small knob in favor of the ball bat muffler but I have since learned over the years that while the ball bat muffler was the main muffler used, the small knob muffler never went away. I recently saw an example of a stamped Feb 68 drum that had only small round knob mufflers. I also owned a set once from July 68 that had dual mufflers with the top mufflers being the large one and the bottom one being the small ones. I have also seen Ludwig use up the small mufflers on acrolites going in to the early 70's. As far as I know the small round knobs were phased out in the early 70's. I'm not positive on that though. Ludwig still makes the large ones today.

Thanks! That information is very helpful.

The small round knob mufflers are found on many marching drums made during the baseball bat era.

Just some more info:

It seems the red felt on the baseball bat muffle was used up to and including 1964. 1965-67 used the white felt.

Two drums that I have owned stamped 1960 and 1961 both had small knobs.

Red felts also continued into 1965. During the first few months of '65 the red and white felts were used together. I assume this ended when the stock of the red felt mufflers was exhausted.