A very brief history for those that may not know the history of the Ludwig Super vs. Slingerland DuAll battle: Ludwig & Ludwig had the patent (1924) for their parallel (Super-Ludwig) mechanism. Along comes Slingerland with their version of a parallel mechanism that they called the DuAll model. Ludwig felt that Slingerland’s DuAll mechanism was infringing on their Super-Ludwig mechanism so they sued Slingerland and won. The court ordered Slingerland to discontinue their DuAll model and I seem to remember reading that Slingerland had to pay L & L the money that was made on their sales of the DuAll models. DuAlls were in production for less than two years so these snare drums are extremely rare.