It's the finish that's referred to as "Mary Kaye" after a female guitarist of the same name. She played in an early 1950's band caled "Mary Kaye Trio". M.K. appeared in an add for the Fender Strat with a trans white/blonde finish. It became known as the Mary Kaye Strat....thus M.K. finish.
Well thanks for the insight. I actually almost got the white body, black pickgaurd and rosewood fretboard on my sterling, except i saw trans orange, and all i could say was ...wow. and i couldn't take the smile off my face.