One of the oddities in our hobby is the concept that a coin can be "unlisted," in other words, not documented in the major catalogs. For those who collect Roman imperial coins, that means the volumes known as..."Roman Imperial Coins" a series of books that started publishing in the 1920's and ended (I believe) in the very early 1960's, or thereabouts. Updated editions have come out for Volumes I and II, which included many types unknown to those writing the initial volumes. How something is defined as listed or unlisted can depend on how much detail is in the reference work. This concept is addressed in Doug Smith's article, " 'Unlisted' Denarii of Maesa & Elagabalus?" In my almost 20 years in this hobby I have only come across one sestertius for which the references were completely silent - in other words a reverse scene completely unknown to RIC. This was a sestertius of Caracalla, sold a year or two ago by the European company Pecunum. The reverse showed a figure with an ax about to sacrifice a bull, among other details. There is nothing in RIC that described that scene for any year in any metal, hence it was completely unknown. It was also in high grade, which made the coin completely out of the reach of most collectors, myself included. Recently Heritage - it had previously been offered by another company - posted an "unlisted" Septimius Severus sestertius, this one with a stunning "IN CARTH" scene with INDVLGENTIA AVGG, IN CARTH, Dea Caelestis in elaborate headdress riding right on lion, holding thunderbolt & scepter. Although this reverse is known for another year or date, it is is not known for the "IMP XI" ending obverse inscription. The coin is magnificent, especially for someone like me who has tried to specialize in the sestertii of Septimius Severus. However, at $3,700.00 it was well beyond my reach. As usual, this note has skidded all over the place before getting to the point. I just purchased what I am relatively certain is another "unlisted" sestertius of Septimius Severus. The reverse shows Victory walking left with wreath and palm - a common type for Septimius Severus sestertii. However, this reverse is not known with the "IMP X" obverse inscription. For comparison purposes I have also listed another "IMP X" sestertius of Septimius Severus, of PAX, which I had previously posted. One other point - IMP X is from ca. 198 AD. Walking Victory with wreath and palm is unlisted as one of the types with IMP X not only as a sestertius but also is not known for an As or dupondius. One would expect that if a reverse was known for one of these two types it is only a matter of time before a sestertius is found with the same reverse. The Walking Victory type, however, is not known for "IMP X" for any imperial bronze. Oddly enough, this coin came very close to being completely missed - all it would take is a little more wear at the end of the obverse inscription and this coin would have been one of those unidentifiable pieces that this collector would spend hours trying to read. However, here the "X" is clearly visible, as is the "P" before it, from "IMP". And there is no other inscription that matches the remainder of the inscription that fits. Let me add that the hope of a find just like this that is one of the reasons I decided to collect sestertii of the family of Septimius Severus - it may be being "unlisted" doesn't mean much because the series is not well documented (finds in the last decade have made it outdated) but I like looking for coins that aren't in the reference. The great thing about this hobby is that all you need much of the time is the knowledge to know the coin is unusual, and it is that knowledge that makes looking for the coins even more fun. Fortunately, the condition of this coin isn't such that it would generate much demand - still for me it is a wonderful find indeed. Nevertheless, I was figuratively biting my nails waiting for the end of the auction but the bidding was relatively modest. The seller didn't say anything about the coin being unlisted, and it doubtful he knew or even cared. But then again, who would care other than an obsessed collector of ancient coins?