No, not necessarily so, that's why I referred to it as a theory. However, there is more than just the galley
reverse type,
cf. Kö
nig p. 92-93.
I don't think it's correct to deduct from the
SALVS PROVINCIARVM / Rhine god
type that something waterborne happened along the Rhine: this
reverse type is Postumus' first (together with
VICTORIA AVG), struck immediately after the siege of
Cologne, and only refers to the Rhine provinces in general, with the Rhine god and a river boat as emblem. The common
reverse types NEPTVNIO REDVCI and
LAETITIA AVG of 261 AD (
Elmer also refers to an apparently
contemporary PROFECTIO AVGVSTI S C-Sestertius), however, must refer to something waterborne, an important event - yet they are peaceful, so it's doubtful if they can be connected to some sort of action against Pirates. A peaceful visit to
Britain sounds more plausible here, I think, though it must remain unsettled.
Lars