https://rpc.ashmus.ox.ac.uk/countermark/898 

GIC 766

denominational mark Β

oval 

6 x 4 mm 

Tabae (Caria)

This is the only recorded coin of Tabae with a Β on the obverse die which has also been countermarked Β. The style of the Β is markedly different from GIC 765. It is clear that GIC 766 was distinct and later than GIC 765.