Watch List notes:

Antoninus Pius. A.D. 138-161. AE as (27.4 mm, 10.19 g, 11 h). Rome mint, struck A.D. 154-155. ANTONINVS AVG PIVS P P TR P XVIII, laureate head right / BRITANNIA COS IIII, Brittania seated left on rocks, sheild and vexillum to left. RIC 934; BMCRE 1971. VF, irregular flan. Scarce. 

This type was most likely struck in Britain with dies brought from Rome.