Jochen,
Ruzicka 660 is correct, since your coin is from the same
rev. die as the specimen ill. by R., pl.
VII.5.
"Earliest long-bearded
portrait" I take to mean, the first
portrait of
Caracalla to show a full beard, that is immediately after he
had grown it and the engravers began to depict it on the coins.
Calling Caracalla's beard "long" is odd, however, since he is never depicted wearing a truly long beard.
Otherwise,
Ruzicka calls Caracalla's
portraits at
Pautalia "unbearded", "bearded", or "heavily bearded".
One of the major shortcomings of these useful, comprehensive, and generally very perceptive older catalogues: far too few illustrations, especially of the obverses!