Apparently back in those days that was the way peoples initials were monogrammed, with the surname more prominent in the middle and the forenames to either side.Also I was right about the hankie, it said JTM which is the parent company of Piggly Wiggly. Nucky and Eli both think of it as JMT though so dunno, still a weird connection.
The guys real name in the show is Jim Mxxxx* Tolliver. He knows Gaston Means and is blackmailing Means to make him give Nucky false info about "Knox" so Nucky doesn't know just how deep in the shit he potentially is. Nucky's spider sense is tingling over it though because of the sudden disappearance of his old BI contact who appears to have dropped off the face of the earth. Means being a slippery motherfucker just adds to it, he'll switch to Nucky if he senses even the slightest weakness in Tolliver.
*I don't think they've said his middle name on camera yet.