OK, I'm back home, surrounded by my reference books... which aren't actually helping much in this case.

The key identifying mark for this particular coin is the crescent, in between the two stars hovering above the twin's heads - this isn't "normal". Sear's nice new Millennium edition catalogue has dozens of varieties for the Roma/Dioscuri denarius, ranging from 211 BC to the low 100's BC. Later issues are easier to ID and date, because the moneyers began to get egotistical and put their names on their coins. No name or monogram normally means an older issue; this one actually appears to be in among the very earliest types (211-206 BC).
Some searching on Wildwinds finally turned it up: the reference is "RSC anonymous 20i". There are pictures on
this WIldwinds page. "RSC" is Roman Silver Coins, a multi-volume catalogue (which was published by Seaby), which I don't own any volumes of. References in other works are given on the Wildwinds page.
As to catalogue value, Sear lumps RSC Anon 20i in with all the other varieties from this time period, as Sear #39, with the CV "from £60 (VF)", noting that "the symbols are extremely varied, some being of considerable rarity" but not going into further detail.
The Wildwinds page linked above lists 8 specimens of this particular type. Prices attained vary - one particularly scuffed example went on
ebay for $17. The best specimen sold at auction for $625. Most seem to be in the $70 to $200 range.
For the first half of your query (authentication), I'd be reluctant to make a firm judgement. It doesn't look obviously "wrong" to me, and it doesn't seem to be in the
FORVM fakes database. Apart from that, I don't really have the expertise in any one series to comment.
Don't say "infinitely" when you mean "very"; otherwise, you'll have no word left when you want to talk about something really infinite. - C. S. Lewis