Watch List notes:

Nero. AD 54-68. Æ As (29mm, 9.88 g, 6h). Lugdunum (Lyon) mint. Struck circa AD 65. NERO CLAVD CAESAR AVG GERMANICVS, Bare head right, globe at point of neck; c/m: [S]PQR within rectangular incuse / PONTIF MAX [TR POT IMP P P], S C across field, Nero, as Apollo Citharoedus, advancing right, holding and playing lyre. RIC I 416; WCN 543; Lyon 90; for c/m: Pangerl 26. Countermark VF, Host coin: VF, dark gray patina, some roughness, minor smoothing marks.

This rare countermark, S(enatvs) P(opvlvs) Q(ve) R(omanvs), is found almost exclusively on Nero's asses placed horizontally on the imperial neck. It was applied in Gallia Lugdunensis, either by the administration of Julius Vindex, during his revolt, or that of Galba between March and June of AD 68.