Search "byzantine Scyphate", you should find a lot about them. They are common, also called "cup coin" because of their shape.
Mine was under $50 USD Fully Loaded: Manuel I Comnenus, AD 1143-1180 Aspron trachy, 35mm, 4.6g, 6h; Constantinople mint. Obv.: Nimbate Christ, bearded, seated on backless throne facing, wearing pallium and colobium; book of Gospels in his left hand; IC (overlined) and XC (overlined) on either side, no stars in fields. Rev.: MANVHL DECPOT; Manuel, standing facing wearing crown, divitision, and loros, holding globus cruciger in his left hand and labarum in his right hand, is crowned by the nimbate Virgin standing facing, wearing pallium and maphorium.. Reference: SB 1966
Much of the value of these depends on details in the faces. Three figures with clear features surrounded by readable legends can be worth 100x the price of a coin with one blank side and not much on the other. Usually the convex side will be worse than the concave but base metal cups with two decent sides like the one shown by Alegandron are unusual. My best is far from great but still has noses. My legends are not so hot.
