I guess this coin qualifies as a placeholder, although I don't particularly concentrate on Roman coinage to any great extent. It is a sestertius of Faustina Junior. It came in a lot of three sestertii, two of which were quite worn and with varying corrosion. While this coin is not particularly rare, a nicer one for type would be a good addition, if it can be had at a reasonable price (easier said than done). I think this coin is RIC 1635, with the two infants and children on the reverse, but the coin is worn and corroded to the point where this is a guess based on much better examples that I saw online this morning. 22.8 grams 28.5 mm, 6 h.
I bought this budget portrait Sestertius of Tiberius minutes after it was posted on MA Shops. A better one will cost me ten times the amount I paid, so I am quite happy to fill the slot in my collection with this eroded but still collectible artifact. TI CAESAR AVGVSTI F IMPERATOR V - bare head of Tiberius left / ROM ET AVG - The great Altar of Roma and Augustus at Lugdunum, flanked by columns surmounted by statues of Victory right and left, the altar ornamented with row of uncertain objects along the top and three wreaths on the front panel. Sestertius, Lugdunum AD 10-11 (under Augustus) 36,43 mm / 22,06 gr RIC (Augustus) 240; BMCRE (Augustus) 572-3; CBN (Augustus) 1737; Cayon (Los Sestercios del Imperio Romano) 4; Cohen 28; Sear (Roman Coins & Their Values I) 1753