Augustus, AV aureus, ca. 19-18 BC. Moneyer M. Durmius. 21mm, 8.22 g. 

CAESAR AVGVSTVS, laureate head right wreathed with oak.
M DVRMIVS III VIR above and beneath crab holding butterfly in its claws.

RIC I 316; BMCRE 60 = BMCRR Rome 4566; Calicó 133a; Biaggi 158 (this coin). 

Very rare.

With permission of Numismatica Ars Classica auction 31, Oct. 2005.