Elis, Olympia, silver Stater, c.424-420 BC, obverse die signed by 'Da', eagle standing right, wings displayed, holding serpent in beak, [Δ]-A across lower fields, rev. winged thunderbolt with volutes, F-A across fields, 11.51g, 3h (Seltman, Temple 137 [BN/γη]; SNG Copenhagen 365 [these dies]; Pozzi 1831 [these dies]; cf. BCD Olympia 58 [this obverse die] and 54 [this obverse die]; HGC 5, 341). Rare, in NGC holder graded Ch F, strike 4/5, surface 4/5. 

*Note the series/coinage is of Elis, a region with a large city of the same name. Elis was a larger place than Olympia but the arguments for the mint being at Olympia are well-established. These arguments include the fact that all of the coinage refers to Zeus and Hera, whose sanctuaries were in Olympia, whereas there were no temples to these deities in Elis.

FA is the start of the word FΑΛΕOΝ (faleon). It means “of the people of Elis”. F isn’t normally in the Greek alphabet and this is a local dialect.