Watch List notes:

Constans II (641-668). AV Light Solidus of 23 Siliquae, Constantinople mint, 651-654 AD. Obv. d N CONStAN [tINЧS P P AV] Bust facing, wearing crown and chlamys, long beard, globus cruciger in right hand. Rev. VICTO[RIA] AVGЧ A. Cross potent on three steps, BO ΓK in exergue (ΓK ligate). D.O. 24; MIB 44; Sear 979. AV. 4.28 g. 20.50 mm. R. Rare and nearly superb. Intriguing graffito Π / K on obverse left field : misread ΓK monogram of exergual mark? Peripheral minor areas of weakness, otherwise about EF.

The very interesting exergual mark on this rare issue reads BO (normally engraved OB = Obrysium = gold) and ΓK = Greek for Γ (3) and K (20).