Britannicus and Nero, AE17 of Pergamum, Mysia. Struck under Claudius AD 50-54. 3.05 g. 

BRETANNIKOC KAICAR, Draped bust of Britannicus right.
NERWN KAICAR, draped bust of Nero right.

RPC 2371; Imhoof KM 3; SNG Munich 131-132.
Very rare. 

With permission of Numismatica Ars Classica auction 92 Part 2, Lot 2078, May 2016

Ex Bankhaus H. Aufhäuser sale 17, lot 217 (2003)