A few days ago I posted about this Poseidon silver bar, asking if anyone knew what it was. Here's what I learned from looking around the internet.
This is a Mardi Gras doubloon. The image of Poseidon refers to the Poseidon parade, which was an annual event from 1959 to 1995. In 1995 the parade stopped running because the krewe couldn't come up with the money to keep it going. In 2015 another group took up the mantle and started running a parade under the sea god's banner.
Doubloons are made primarily to be thrown from floats during the parade. Back then they were mostly made from aluminum; nowadays they are mostly plastic. In the 60's and 70's it was common for krewes to make a limited number out of other more valuable metals, such as brass, pewter, or even silver. These were not meant to be thrown, but as keepsakes for those participating in the parade. That's likely the origin of this piece.
I've not been able to confirm the identity of the the man on the back, but it seems very likely that he was the king of the Poseidon parade in 1974.
That's what I was able to figure out. If anyone has additional info, I'd like to hear it.