This one is 17.11 mm and weighs 3.94 g. ex Bertolami Auctions. In contrast Legate II 18.27 mm x 17.11 mm 3.13g Ex-Steve Clarke collection. I bought this one because of the oversized flan and for more or less the same reasons as @dougsmit posted on another thread. I was confident that this wouldn't be faked. In my collection of these fleet denarius there is a considerable range of diameters and weights.
Quite surprising and unexpected to see my homeland mentioned in a thread about Marc Antony denarius, this hobby never fails to surprise and please although sometimes the surprises aren't always pleasing!
The OP may look undersized but with quite a good weight for the issue. Mine below is undersized and one gram below... Marcus Antonius, Denarius - Mint travelling with Marcus Antonius, c.32-31 BCE ANT AVG III VIR RPC, Galley right LEG III, Legionary eagle between two standards 2,83 gr Ref : HCRI #350, Cohen #28 Q