This coin, which was found near Amiens, France, is regarded by most auction houses as Celtic, but by others (Les bronzes de Germanus Indutilli L., in : J.-M. DOYEN, Économie, monnaie et société à Reims sous l’Empire romain. Recherches sur la circulation monétaire en Gaule septentrionale intérieure, Reims, 2007/2008 (Archéologie urbaine à Reims 7), p. 63-93.) as Roman Provincial. My French is (very) poor, so perhaps someone with either better knowledge of French or this specific coin could weigh in: CELTS, Germanus Indutilli Libertalis. Denomination: AE Semis, minted: Gallia Belgica; c. 27 BC to 14 AD Obv: Diademed head of Germanus Indutilli to the right Rev: GERMANVS (above) INVTILLI L (in exergue) Bull trampling to the left Weight: 2.94g; Ø:16mm. Catalogue: RPC I 506; RIC I 249. Provenance: Found near Amiens, France; acq.: 08-2020 From "Le semis de Germanus Indutilli L." by Jean-Marc Doyen: "This sometimes classic-style bronze, made from an alloy containing on average 12% zinc (orichalcum) is a semis and not a quadrans as has long been assumed; it is cut to 1 / 108th of a pound (9 dozen). The distribution map shows a distribution following fairly closely the boundaries of the new province of Gallia Belgica, for which it serves as an additional coinage. Traditionally classified as a Gallic coin, this bronze is actually a provincial issue made in Reims under imperial control by a Reme prince by the name of Indutillus. The latter entrusted the task of signing the program, in the manner of Augustus or Tiberius, to a freedman named Germanus. The obverse shows the portrait of Indutillus wearing the royal diadem (which Augustus never dared to do). The reverse presents a strapped bull (detail forgotten on Dardel's drawing in the Atlas by H. de La Tour, like the royal diadem, transformed into a laurel wreath), an element that can be found in the following Reims series ( RPC 509), drawing inspiration from Lyon's “charging bull” funds. In general, the iconographic prototype of the reverse of Germanus Indutilli L.'s bronze must be sought in rare aurei of the RIC 538 type, probably issued in Gaul after 27 BC. J.-C."
It's a debatable point, since there doesn't appear to be enough evidence either way. The mint is uncertain, who is depicted is uncertain and it's not even clear who Indutillus or Germanus were. What is meant by 'provincial' is also debatable. In a new province, the pre-Roman coins might continue to be minted. Other times, the Romans just let the locals get on with it and mint their own bronzes (such as the barbarous issues in Britain and Gaul). For a coin to be provincial, though, I would imagine it should be minted under the civic authority of that province (e.g. the governor), and not just in the province. Even then there might be doubt. Indutillus might have been a local tribal leader given authority to mint coins by Rome. And of course, Roman politics was a messy and ever-changing business - it's sometimes not clear who was in charge at all.
An interesting and well preserved coin. The pose of the bull reminds me of this coin from ~300 years earlier - no question what a bull looks like charging. Sicily, Syracuse, struck under Hieron II(?), AE 17.5mm, 275-269/265 BC, 6.04g Obv: [ΣYPAKO]ΣIΩN, head of Persephone left, crowned with wheat; behind, amphora(?) Rev: Bull butting left; and I; in exergue
Thanks all for the interesting comments. I've decided to label it as "Celtic" for no particular reason other than that I need to label it with something