What a great coin. I have seen nothing like it.
I suspect though that the consulship of 342 is more likely than 339.
You are right that PF appears in the late 330s at most mints. Circa 339 is a
good guess as it appears mid-way though the series of Constans' post-accession
mint marks. In other words mid-way between September 337 and early 341.
However,
Rome breaks this pattern. Your exact
obverse legend DN FL
CONSTANS AVG is used at
Rome only after the end of the
GLORIA EXERCITVS et all series - thus after early 341. It is used on the first few issues of the two victories
type -
VICTORIAE DD AVGG Q NN. It is used on the two issues of the variant with both victories advancing left (R P and R
P), which was likely struck first, and then on the first issue with the two victories facing each other (R P). That issue then switched to
CONSTANS PF AVG.
I believe (as laid out in a forthcoming
work) that a wide variety of
victory types were struck at different mints in 341 and that in 342, after the start of the shared consulship and likely at the time of the reported "split" between the two brothers, the
types were simplified with the two victories facing in the
West and the new
vota type in the East.
The
types of 341 include the one
victory types like
VICTORIA AVGVSTORVM at
Lugdunum,
VICTORIA AVGG at
Aquileia and
Siscia, and
VICTORIA AVG at the Eastern mints as well as Rome's two victories left.
Yours ties into this perfectly. If regular issue with worn
mint mark it would add the single
victory type to
Rome too. If, as more likely given the
obverse bust and lack of visible
mint mark, it is a special medallic issue, then it
still is a perfect stylictis match for an issue circa December 341 / January 342.
As a wild card I would also point out RIC-VIII-Rome-56. This coin, which
Kent notes need confirmation and is with uncertain
legend break, is reportedly a
Constantine II with VIC
CONSTANTINVS AVG and regular draped
bust with
reverse VICTORIA AVG victory advancing left and no
mint mark. In other words it appears to be your exact
reverse.
Does this coin really exist as described? Could it be with consular
bust too? Could it be for Constantius instead??? Confirmation of this could could
help resolve the dating of yours.
Kent lists it as
G, which I think means it is from Voetter's book on the
Gerin collection and therefore should be in
Vienna. The fact
Kent could not confirm it calls it into question.
SC