Michael, technically speaking there’s no such thing as a Mark IV. it’s actually a Balanced Action model. These were excellent horns nevertheless and they preceed the Mark V1. I’ve Heard of one going for $6200. I’ve never triedd playing one so can’t tell you how they compare to a Mark VI.
Get the serial # and go check it out on this site: http://www.saxophone.org/museum/serialNumbers#manufacturer-1
