Without it in hand nor seeing the edges, I'm still inclined to say it looks legit to my amateur eye. Plus, it looks a heck of a lot better than mine!
It looks good to me, but I'm no expert. This is a fairly common late Republican issue that I think very attractive - unfortunately they are hard to find not worn down or badly struck. Ryro's is better than many I've seen, but the mostly missing second head on the obverse seems to be a common striking/wear problem. The OP is a pretty nice one. Here is mine - one of my first ancients, pre-Internet, 1990. I bought it from Bill McDaniels, who sold budget ancients from an (unillustrated) paper price list - I was always happy with my purchases and prices from Bill (this was $32). A bit off center and a big banker's mark - about as good as they get in my RR collection: Roman Republic Denarius Mn Cordius Rufus (46 B.C.) RVFVS III VIR, conjoined heads of the Dioscuri right, in pilei, stars above / Venus Verticordia w. scales & scepter, Cupid on shoulder MN CORDIVS behind. Cordia 2a; Cr463/1a; Syd 976 (3.67 grams / 18 mm)
Weight? Diameter? Edge view? Do you know/trust the Seller? Check Forum Fake list? (Or other lists). I also check acsearch.com for similarities and/discrepencies.
MN. FONTEIUS ROMAN REPUBLIC; GENS FONTEIA AR Denarius OBVERSE: Jugate heads of the Dioscuri REVERSE: Galley under oar Struck at Rome 108-109 BC 3.9g, 20mm Cr.307/1, Fonteia 7
It's beautiful but be careful with it. It appears to have a fault line running through the top from 12 to 2 o'clock.
A long time dealer/friend pointed this out to me thinking I would find it interesting. He was right! We see Castor and Pollux riding, standing and as jugate heads but rarely will you see them just sitting their taking life easy. Caracalla 4 assaria Tomis