I've been researching this new acquisition, and haven't been able to find a reference to it in Dattari (the original edition, no access to Savio) or any auctions that I've checked. Since the university semester is over I can't make a trip to the library to check RPC there, but if anyone has access to it would they mind checking for it? There are several issues with the same reverse which are very close (Dattari 618-624), but none that are the same. The date appears to be, to my eyes, Year 6 (LS), but Dattari has that date as being present only on the obverse (Dattari 621), whereas mine is on the obverse. Has this coin been published previously?
I think all but a couple years are published. I cant see anything on yours. Oh. Wait, I see it now. I'd have to look at some actual books. Might not have time for a couple hours. Maybe someone will answer before then.
What's the size and weight? Assuming it is an obol, it is Emmett 317. That reverse was struck in regnal years 2 through 12 plus year 14.
Do you mean in references, or on the coin itself? The date is on the obverse, rather than the usual obverse. It's directly by the neck of the bust. EDIT: And in answer to @TIF, it is 20mm, 5.24g, which I think would be an obol. And like I said, Dattari does list a Year 6 obol with the same reverse, but states that the date is listed on the obverse, beside the falcon, rather than on the obverse as with this one.
Emmett's system focuses almost entirely on the reverse, with some secondary ways to notate types of obverses. He doesn't assign different catalog numbers for variations of legends, date placement, secondary devices, etc. Emmett 317 would be any Domitian obol with hawk right reverse.
Milne catalogs a Domitian obol/hawk right with LS on the obverse instead of reverse; Milne 488 (Milne 487 is the same but with the date on the reverse).