As Dusty asked please post a picture of where it says it is a Mark IV. Include one of the Belt Cover Vent Plate and if it has one because it was made in December 1987 or later, the serial & model number on the separate sticker.
Mark IV shows up from time to time in listings but I have yet to see one that is actually a Mark IV instead of being misnamed.
Mark V 520 S/N 09-11-01 completely upgraded to Mark 7, with all SPT's & more.
Model 10ER S/N R64000 first one I restored on bench w/ Shopsmith metal ends & retractable casters. Has Speed Changer, Model 4E Jointer, Jig Saw with lamp, a complete set of original accessories & much more.
Model 10E S/N 1077 oldest one I have restored. On bench w/ Shopsmith metal ends & retractable casters.