This emission and this coin are fascinating at a number of levels. On this coin, the obverse in top left field (10:00) contains an almost complete letter “A” - Hirsch Auc 256 lot 183 appears similar.

The “A” between the confronting boar heads (some suggest) indicates the Lesbos city/municipality of Antissa, although on billon coinage the letters “A-N” have been taken to denote Antissa. This is the only emission in the hecte series for Mytilene to have the single letter “A.” The previous emission listed by Bodenstedt, B44, has the same obverse with the reverse sometimes having the letter “M” above a bull’s head facing left. The “M” has been taken to indicate Mytilene. A somewhat ‘parallel’ to the reverse design of this coin, B45a, is noted in Bodenstedt 35, where there are confronting heads which have different letters between the heads.

Lazzarini (“A contribution to the study of the archaic billion coinage of Lesbos”, Obolos 9(2010) 83-111, p.96) has cast doubt that such letters are simply confined to indicating a city, but argues the letters may also indicate the name of some important figure or monetary magistrate (see CNG Triton XVIII, lot 590).

In the hecte series for Mytilene we find confronting (facing), conjoined or overlapping same human or animal heads on the reverse of emissions B35, B37, B45, B50, B55, and B57. This feature is also to be found on billon coinage of Lesbos. At one point, Lazzarini suggests the facing heads may be simply to represent a pact of some kind between cities of the island.

Update: Walter Holt (of "oldmoney" on Vcoins) has pointed to Triton XIX Lot 188, B44 which seems to share the same obverse die as the coin described above but is in a deteriorated state with die rust - thus, he comes to the sensible conclusion that B45 should be before B44 in the chronology of these emissions.