Unsurprisingly, I don't know this coin and it took a bit of time to identify it even with the moneyer's name visible. Marcus Arrius Secundus, Crawford 513/3, known from only one obverse and one reverse die?
Mostly I focus on collecting what catches my eye. Having said that I have been working on a 3rd century set and am getting close to rounding out a run from Gordian - Aurelian. There will likely be a few empty spots in terms of usurpers but I don't see myself affording a Zenobia (but that would be very cool! And not in the current budget at all) Not sure Marius will make the cut. Just got a Aureolus (Postumus portrait) that I am quite happy with and recently posted Hostilian and Aemilius that have taken some patience to get.
Not just known from a single pair of dies. Ho-hum, lol! It's more amazing than that. As far as anyone knew (other than the owner of this piece, obviously, and anyone they let in on the secret) the only two extant examples of the type were in public collections, in Bologna and in the Capitoline Museum in Rome. (I have about a million pics of the latter specimen, taken through the glass. I've attached one here.) The type is missing in Paris, missing in London, missing in Berlin, missing in the ANS, missing in Haeberlin and every other private collection any of us knew about... except, obviously, one anonymous collection. This example wasn't "supposed" to exist. There are a couple of RR denarii even more rare, known in just a single example.
The reverse scene is more interesting than it appears at a glance. It depicts an episode from the Servile War against Spartacus, in which the moneyer's father Quintus Arrius seized a standard from the soldier carrying it and threw it into the midst of Spartacus' forces. Quintus knew his men; he was confident that the Roman soldiers, whose devotion to their standards was well known, would have no choice but to charge the enemy lines to retrieve it.
Since I specialise, many of my collection 'holes' would not be of interest for 99% of collectors. I won't bore you by listing my personal sought after RIC numbers. However, if there is one general area in my niche I would like to remedy someday it would be by adding a few coins of Flavian ladies. I'm long overdue on this front.