Watch List notes:

EGYPT, Alexandria. Commodus. AD 177-192. BI Tetradrachm (24mm, 11.88 g, 1h). Dated RY 33 of Marcus Aurelius (AD 192/3). Laureate head right / Serapis enthroned left, holding scepter; at his feet, Kerberos seated left, two Nikai holding wreathes atop throne, crowning Serapis; L ΛΓ (date) to left. BMC Supp. 3114, pl. 8; Köln –; Dattari (Savio) 9588; K&G 41.141; RPC IV Online 14230; Emmett 2557.33 (R4). Very high silver content, edge nicks, some surface porosity. Near VF. Very rare type for this regnal year, which is Commodus' last. Extremely rare variety.

From the Rocky Mountain Collection of Alexandrian Coins.

RPC only lists 11 specimens of this type, however ten of them have plain thrones. Only one, described in the BMC supplement, shows the Nikai atop the throne. The only other reference I could find to make that distinction is Dattari.