That's the iconic harp that so much great playing was done on - by pros, making it a pro harp. And many current pros love the sound of the Marine Band.
Rounding off the comb tines, sealing the wood, and using screw construction, as is done in the MB Deluxe and Crossover, updates the archaic parts of the Marine Band build. And many customizers continue to prefer the Marine Band as a platform for their builds. Could be something more than blind adherence to tradition. =========== Winslow