For a discussion of the identity of the obv. head, see introduction. A coin is cited in the note from D108, with the comment (see also RPC p. 698) that the date is more likely to be year 3 than the year 4 given in D’s text. DS 108 shows that the date is actually off flan! There is thus no evidence for pieces of year 4. See A. Burnett, 'The Alexandrian coinage of Caligula', in D. Gerin, A. Geissen and M. Amandry (eds), Aegyptiaca serta in Soheir Bakhoum memoriam. Mélanges de numismatique, d’iconographie et d’histoire, Collezioni Numismatiche 7 (Milano, 2008), pp. 45-7.