I was a little worried about the fragility of this coin when I bid on it and was pleasantly surprised see that, in hand, the flan crack that looks cavernous in the photo is very stable, and for me not distracting.
Roman Republic, Anonymous AR Quinarius, 211 BC
Mint: Rome
Obv: Helmeted head of Roma right; V behind.
Rev: The Dioscuri on horseback to right, ROMA in linear frame in exergue.
Ref: Crawford 44/6; Sydenham 141; RSC 3.
Size: 15.6mm, 2.21g (1/2 denarius, weight standard based on denarius weight of 4.5g)
A few quotes on the time period from Kenneth Harl, "Coinage in the Roman Economy":
"In the Second Punic War, the Republic reforged silver and bronze currency into a system of denominations that endured for the next 450 years"
"Roman triumphs on the battlefield also ensured the triumph of the new Roman currency throughout Italy and the provinces of Sicily"
"Hundreds of thousands of gold and silver litrae of Syracuse, Corinthian-style pegasi, Campanian and Italiot didrachmae, and sheckels of Carthage and her Italian allies were melted down and struck into denarii in massive re-coinages in 211-200 B.C. that changed the face of currency in the western Mediterranean"
The coin above illustrates the quinarius version of the A2 helmet style referencing this Sydenham table (Hersh p.78) which is an early helmet style.
Interesting to consider where the silver for this quinarius might have come from.
See Steve Brinkman's site, an excellent resource for these coins, see the page on RRC 44/5 IX.22 - group 5. No quinarii are known so far for group 6 and group 6 denarii tend to have a solid visor (rather than 3 splayed lines) . Distinguishing characteristics:
Large head of good style and natural uniformity, curved splayed visor (Sydenham Helmet A.2) although the quinarius lacks the spikes on helmet.
Reverse Horse’s tail hangs down from behind the closest horse
The legend ROMA is semi-incuse (although not on the quinarii). Usually the frame is without a left side and enclosed
Last in Crawford's Plates here is the relevant denarius (22-44/5) + quinarius (23-44/6):
Flan cracks have never been a problem to me unless they are significant enough to actually break (extremely rare with early republican silver), or if they obscure the design. Yours doesn't distract and its a very representative quinarius example. I think perhaps this particular quinarius variety is the latest in the RRC 44 series as no sestertii are known with this style, RRC plate IX.22.