Cr. 64/6a MA series Æ Sextans, 210 B.C., Sardinian mint
Roman Republic Æ Sextans(18mm, 3.24 g, 1h). Publius Manlius Vulso, Praetor of Sardinia, 210 BC. Sardinian mint. Head of Mercury right; above, two pellets / Prow right; above, ROMA; (MA) vertical to right; two pellets below. Crawford 64/6a; Sydenham 160c; Russo RBW 269-270
Overstruck on Sardinia, Punic Occupation Tanit/Bull with star, cf SNG Copenhagen 387-388. For sextans with MA overstruck on Tanit/bull with star, cf Hersh, Numismatic Chronicle 1953, 17; Crawford, overstrikes 49
Ex Andrew McCabe Collection, AM#1316-32, CNG e-auction 452, 9/18/19, lot 665, ex RBW Collection, ex Fallani Collection, Vecchi 3, 9/13/1996, lot 175
This sextans comes from the series of coins struck by the Sardinian Praetors of 211-209 B.C.(there's actually a fourth "spearhead" type too but no one's certain when in the timeline it was struck). In this case the coin has an "MA" ligature to right of the prow, generally interpreted to be the mark of Publius Manlius Vulso, Praetor of Sardinia in 210 B.C.. These coins often show signs of overstriking but it's not always obvious what they're overstruck on, in fact none of my other Sardinian Praetor sextantes have decipherable undertypes. In this case, however, there's one really good hint as to what the undertype is: a star on Mercury's neck which tells us that the undertype is almost certainly a Sardo-Punic bronze with Tanit on the obverse and a bull with a large star above on the reverse, like this one(the bottom coin in my picture). The Sardo-Punic undertype would likely have been struck just a tad earlier in the war, circa 215 B.C. as the Carthaginians were landing on Sardinia and attempting to take the island. The Carthaginians were, of course, ultimately unsuccessful in this attempt. These coins are fairly common so the Romans must have captured a considerable amount of bronze coinage during this fighting.
I've illustrated the orientation of the undertype below my coin here to make the overstriking more obvious. The bottom coin is of course not mine but is one of the best examples I could find of the undertype. Figuring out how Tanit's head lines up with the reverse was a bit more difficult than figuring out the obverse due to the placement of the star but you can see a bit of Tanit's neck and chin at 6 o'clock in the photo of my coin. There's also a bit of Tanit's ear and earring visible just right of center on the reverse.
Image copyright Classical Numismatic Group