AE Semis
Some info about this
semis since I'm the one who purchased it: This coin is actually not an official
Rome mint semis but instead, an imitation, likely struck in
Italy during the first century B.C. to address a small change shortage. The
Rome mint cut back on its bronze output considerably during the latter half of the second century B.C. so while large numbers of
denarii were being minted, the bronzes that citizens used for day-to-day transactions were in short supply outside of the city of
Rome itself so, in similar fashion to the Civil War Tokens that many U.S. collectors are familiar with, private individuals or perhaps even city governments began striking imitations on a similar
weight standard and with similar designs as
Roman bronzes, in many cases re-using old
mintmarks such as the
dolphin on this coin. The
Roman government was probably perfectly
fine for this and may have even encouraged it as the
Rome mint could focus on striking precious metal
denominations which were far more useful for the
Roman government itself.
As an interesting note: this example is an
obverse die match to the British Museum example which, when
BMC RR was originally published was actually thought to be an official
Rome mint product(though they were obviously somewhat unsure of its status as it wasn't included in the main arrangement but instead, the appendix at the end of
Vol. 2). They've changed their minds since then and the coin is now listed on their website and in more recent updates of
BMC RR as an imitation, but it's an interesting footnote in the
history of this particular imitation.