Jimmy,
EX/MT has been around since as long as I have collected (1970s) or Ex to Mint as you posted. Can't really explain it other than it has been a standard grade for a long time and has always been understood to be less then NR-MT and of course better than EX.
Sorry I could not impart more wisdom than that but it's not an error or a mistake. To me it has always made perfect sense as that grade implies a grade halfway between EX and Mint hence the EX-MT. NR/MT is then halfway between EX-MT and MINT or thereabouts....
Mike
Last edited by vthobby; 08-12-2015 at 06:47 PM.
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