A palm twig, I think.
I came across this picture, which is of a
Roman marble copy preserved in the
Vatican Museum of Eutychides' original bronze
Tyche of Antioch statue. That makes it clear she is holding ears of
corn (grain). And the
poor Spirit of the
Orontes looks a
bit down-trodden, don't you think?
One's first reaction is that the appearance of Tyche on a sixth-century coin is a very curious survival of pagan iconography. But maybe in Antioch by the time of Justinian the Tyche statue was no longer thought of as a religious artefact, but merely as a tourist attraction (like the
Serpent Column in Constantinople's Hippodrome).
Bill R