to customers. Some horns built from extra parts or reconfigured bear an X on the serial number on the second valve casing, others had a digit added to the original serial number. In some cases, the same serial number exists on another horn. After WWII, Bach was similarly creative in the first years with manpower and material shortages. The wrap height increased slightly during these years, and the tuning slide while still a "D" shape, became correspondingly flatter. Mount Vernon Period Early Mt. Vernon Time frame: 1953–1956 Products: Mouthpieces, Brass Instruments Brand names: Stradivarius, Mercury, Minerva, Mercedes Location: 50 South MacQuesten Parkway, Mount Vernon, New York Serial Numbers: 12,600 – 16,000 (approximate) Over the years, the company produced several ranges of trumpets, cornets, flugelhorns and trombones, using the brand names Apollo, Minerva, Mercury, Mercedes and Stradivarius. The Vincent Bach Corporation moved in 1953 from New York City to Mount Vernon, New York. Mt. Vernon Bach horns are prized for being hand-assembled instruments. Mt. Vernon horns can be identified by the Bach manufacturing stamp listing Mount Vernon NY on the second valve casing along with the bore letter code and serial number. At first, the instruments built at the new factory were identical to the bulk of what had been produced the few years before These were typified by the same wrap height and .020" bell stock Bach had been using primarily after the war. Mt. Vernon Time frame: 1956–1963 Products: Mouthpieces, Brass Instruments Brand names: Stradivarius, Mercury, Minerva, Mercedes Location: 50 South MacQuesten Parkway, Mount Vernon, New York Serial Numbers: 16,000 – 25,000 (approximate) It is instruments and mouthpieces from this Bach era that are still aggressively sought-after by many who believe that none-other are of this quality. However, several Bach periods each have their fans and the Mt. Vernon mystique is in part due to the early advocacy of these in particular. The design of the trumpet changed at this point in time to include the full wrap height still built today, to feature a flat-faced tuning slide, and to one which required the tuning slide be pulled an inch rather than the customary 1/2 inch to be in tune. This last, by some workings of the physics, is said to "loosen the centering" and "open the blow" (make it take less energy to match pitch with others and make the horn respond). Selmer at Mt. Vernon Time frame: