The "Reference 54" refers to the modern recreation of their legendary Mark VI, which began production in 1954. When we received the first of these horns, we conducted extensive play test comparisons. When comparing this horn to Mark VI's with serial numbers ranging from 5-digits to the last of the line, this horn stacked up magnificently and, at the very least, gave every Mark VI a run for the money. This horn is sure to reveal itself as a solid modern alternative to the Mark VI with a consistency that had, up to this point, been considered unattainable.