From the Harlan J Berk vcoins.com store:
http://www.vcoins.com/ancient/harlanjberk/store/dynamicIndex.asp


Tranquillina, Denarius

Denarius, Rome, 241 AD, 3.31g. RIC-252 (R4). Obv: SABINIA TRANQVILLINA AVG Bust diademed, draped, r. Rx: CONCORDIA AVGG Concordia seated l. on high-backed throne, holding patera and double cornucopia. Extremely rare, both as a Rome-mint coin of Tranquillina and for its denomination. There are only three specimens of this denarius in Berk photofile, all from different obverse and reverse dies than each other and than our coin. Cohen 1 values the corresponding antoninianus of Tranquillina at 800 francs, but the denarius was unknown to him. Gordian III had struck denarii as his regular silver denomination for a few months in 240, but by 241 when he married Tranquillina he had reverted to the antoninianus as standard silver coin, and the denarius had become an extremely rare special denomination probably struck for distribution on special occasions, like the silver quinarius. Near Mint State. This is the first denarius of Tranquillina we have handled in 41 years. Struck on the broadest flan of any of the known examples with almost full borders of dots on both sides. Probably only the 4th specimen

 Price  
  US$ 20,000   euro 15708.31
 £ 10759.96
 AUD$ 25954.06
 CHF 24517.27
 CAD$ 22144.00
 
Rates for 5/5/2006