Pergamon, Mysia AE Athena/Trophy with Hercules Club Countermark. Help?

I recently got this little bronze from Mysia in Pergamon, a common one with Athena and a trophy. It has been countermarked with what looks like a club of Hercules on the reverse. I have scoured the online sources and have found a couple of countermarked Pergamon bronzes - Doug and Bing have some nice ones that have been posted here - but no clubs that I could find.

I was wondering if there is any info out there about this? Other examples? Also, any info on Pergamon countermarking practices in particular?

Many thanks!





Pergamum, Mysia Æ 19
(c. 200-27 B.C.)
Helmeted head of Athena right / AΘHNA[Σ] [N]IKHΦOΡO[Y] to left and right of trophy of arms. O on ΔI monogram in left field.
Weber 5198; BMC 179.
Countermark: club of Hercules (?)
(4.87 grams / 17 x 19 mm)