The Legion denarii are not difficult to find and those of the III Legion are one of the commonest. However, they are rare in such a high grade as the one now in the auction. We can take as reference price this beautiful specimen ($1100). We can also take references of high-grade denarii in the name of other common legions such as this one (900 GBP) and this one ($2000). Then, 900-1200 GBP would be a reasonable hammer price interval.
Description from the seller
M. Antonius, Denarius, Mint moving with Antonius, 32-31 BC; AR (g 3,74; mm 16; h 6); Ship r., with sceptre tied fillet on prow; above, ANT AVG; below, III VIR R P C, Rv. eagle between two standards; below, LEG – III. Crawford 544/15; Antonia 107; Sydenham 1220. Lustrous, about fdc.