Constantine II, as Caesar AD 317-337. AE3 Nummus. Nicomedia mint, 6th officina, c. AD 328-329.

Obv: CONSTANTINVS IVN NOB C, laureate, draped and cuirassed bust right.

Rev: PROVIDENTIAE AVGG, campgate with two turrets, star above; in exergue SMNS.

Weight 2.70 g, approx. 18-19 mm, die axis ∼6h. Dark green patina with earthen highlights, good VF, minor roughness on reverse fields as struck. Nice sharp campgate detail — the two turrets and star are clear in hand (see photos).

This is a contemporary mule. The obverse is pure Constantine II Caesar, but the reverse legend is the Augustus issue PROVIDENTIAE AVGG — "in honor of the foresight of the emperors" — normally paired with Constantine I at Nicomedia. Hybrids like this are documented for the campgate series, for example a Trier Constantine II with an AVGG reverse noted as a hybrid with Constantine I's type.

References: cf. RIC VII Nicomedia 157 (Constantine II, PROVIDENTIAE CAES•, SMNS, 2.55g, 328-329) ; and RIC VII Nicomedia 153 (Constantine I, PROVIDENTIAE AVGG, SMNS, 2.63g). Your 2.7g sits right between the published Nicomedia weights of 2.55-2.67g for this series.