Watch List notes:

Egypt, Alexandria. Antoninus Pius. A.D. 138-161. BI tetradrachm (23.2 mm, 11.58 g, 12 h). Alexandria mint , Struck A.D. 156/7. ANTωNINOC CЄ-B ЄVCЄB, laureate head of Antoninus Pius left / Nilus reclining left on sphinx, holding reed and poppy; on left Euthenia (Pax) standing right holds wreath aloft; to left, K / L ( = yr. 20 = A.D. 156/7 ). Emmett 1416. VF, ancient edge chip 7:00 obverse. Extremely Rare (Emmet freqency "5" = Rarest). 

From the D. Thomas Collection. 

Struck in Regnal Year 20 only