An interesting coin, that until now I hadn't known existed!
BMC p. 236, note *, reports such a
dupondius as being in Naples, but casts doubt on the correctness of the reading MACELLVS.
In MacDowall's
Nero and Sutherland's
RIC I, I find no mention of the
legend MACELLVS
AVGVST. However,
MacDowall 189, taken over by
RIC 189 (coincidentally the same
catalogue number in both works), reports a
dupondius with the same
obv. legend and
bust type and with the
Macellum rev. type, but supposedly
legend MAC AVG, as being in that same
collection, Naples, and nowhere else. I think it very likely that this is the same MACELLVS
AVGVST coin described in
BMC, but with the extraordinary
rev. legend unfortunately not recorded.
Now, the Naples
collection was stolen in 1977. Some of the coins were recovered, but if their MACELLVS
AVGVST dupondius wasn't among them, I think it very likely that you now own the Naples coin! Your ownership should be secure, however, since there is no way to prove this hypothesis; the museum didn't possess photographs of its coin
collection. Could you tell us where and when you acquired the coin, and incidentally its
weight and
die axis?
As to the
legend, I wonder whether MACELLVS might not be a correct alternative masculine form for the neuter MACELLVM, which is perhaps attested only on this
dupondius. One wouldn't expect a spelling error on a
Roman coin of this era. For a
Roman to get the gender of a word wrong would be like an English speaker referring to a woman as "him" or "it"! This was apparently the first labeled
Macellum reverse die. The
type had indeed appeared in the preceding issue without S C or mark of value, but there it was unlabeled, so the
type was entirely
anepigraphic. Your coin has S C and mark of value II, and the earliest form of
obv. legend in this issue, with
CLAVDIVS and
GERM. So MACELLVS
AVGVST was apparently the
mint of Rome's first attempt to label this
type, and the
legend was then abbreviated to just
MAC AVG on all later
reverse dies.
