MKM closed their doors in 1980 before 853 came out, I don't recall them being accredited for 753 so that would make the frame most likely a 531 variant, matching the Dominator road frame.
You are most likely right I'm not near the frame when I was writing the post . I do know we got the right decals that matched the ones that were originally on the frame before powder coating it .
531 sounds right...although the Feb. 1980 price list does quote for 753 tubing so they must have been accredited.(Having said that I've never seen an MKM frame built in it)
D.