Some of the the busts are recorded in RIC with an H underneath, so it's not an irregularity. This coin is RIC VI 214a, p. 183. As to its meaning, I don't know, but perhaps the analysis at the beginning of the Treveri mint chapter gives us a clue. It's long, however, and I'm going to bed, so I'll read through it tomorrow.
Wow, Noob => your OP-coin has great colour (sweet eye-appeal) *Rats* ... my example doesn't seem to have an "H" on it (sigh, I need more coins)
