I also gathered information for this page from website that cites Albert Mensinga as the source for MANY of the serial numbers. I do not know if an Elkhart Serial number list exists or not.
Most (if not all) Buescher trumpets that have the ELK logo have a separate serial number listing. These are most likely mid to late 1960s instruments. Most seem to have the Upsidedown Nike Bell Logo and are model BU-7. Buescher Elkhart Alto Saxophone S Serial Number Here As.