I found these other examples of the strange coin of Augustus and Agrippa mentioned earlier today - and none of them have the pig's leg attached. The issue was clearly designed to be anti-Egypt, anti-Cleopatra propaganda, but why the Nimes example(s) had a pig's leg added to it (the join can be seen clearly on the obverse in this larger image), I still cannot work out. The books I've looked up are not 100 % clear, but there seem to be other coins found at Nimes, also with hind legs added, and excavated coated in mud - the interpretation is that they were thrown into the source of the town's water / a fountain, for votive reasons.
Agrippa of course was the admiral at Actium, where Anthony and Cleopatra where defeated (31 BC); many veterans from the campaign settled in Colonia Nemausus and the province.
Interestingly, before the Colony was founded by Tiberius Nero (Livia's first husband), the town had supported Sertorius, a Marian rebel in Spain. The town, founded by the Greeks, stood on the Via Domitia, the main road from Italy to Spain, so was important strategically for Gaius Marius' follwer.