This Sestertius was sold to me as a Septimus Severus with Concordia seated, but I believe it to be Antoninus Pius with Ops. Am I right? What do you think? (Seller's pictures)
I agree with TC's take on the reverse figure. Ops comes on Pius and Pertinax. Pertinax is easier to find but costs more.
ops is possibly the reverse... something like this, but the break on the obv legend is different. RIC 612 sear5 #4197 Antoninus Pius Sestertius. ANTONINVS AVG PIVS P P TR P COS III, laureate head right / OPI AVG S-C, Ops enthroned left with transverse sceptre & drawing up drapery from shoulder. Cohen 569.
However, YOC if you look at the second coin in your link the the break in the obverse legend is the same. I am leaning strongly towards RIC III 612a for an attribution for this coin. I know that the coin is not an 'excellent example' but for US$12 I am happy.
this is the bumph which went with it Coin Type: Brass sestertius of Antoninus Pius, Caesar 138 CE, Augustus 138-161 CE Mint and Date: Rome, 142 CE. Size and Weight: 29mm x 31mm, 21.31g Obverse: ANTONINVS AVG PIVS P P TR P COS III Laureate head right. Reverse: OPI AVG Ops enthroned left, transverse sceptre in right hand,drawing up drapery from shoulder with left hand. Flower at back of chair. Exergue: S C Provenance: mckenzie7835 (eBay), May 2008 Ref:RCV (2002) 4197; RIC III 612. BW Ref: 024 052 127