They would have established themselves in this area during the Celtic migrations at the end of the 4th century BC, though there is no evidence for their existence before the 1st century BC. Serdi are among traditional tribal names reported into the Roman era. They were gradually Thracianized over the centuries but retained their Celtic character in material culture up to a late date.
The Serdi struck coins imitating various Macedonian issues. Like other Celtic coinage, the imitations were not meant to be counterfeits but were used as local coinage.
Reverse: Wide trident
Die Orientation: -
Weight: 8.37 g
Celtic imitation of Macedonian issue from 185-168 BC. Overstrike of Thessalonica, 187-31 BC, head of Dionysos with ivy wreath right, goat standing right, ΘEΣΣA_ΛO / N_IK_HΣ, (NE) / ? other monograms, Sear #1466; BMC Macedonia p. 110, 10 - 16. Head of goat and one ivy-leaf under Strymon's head are slightly visible. Imitations from Serdi region weren't used to fool Macedonian traders but as their own currency. This coin is one of overstrikes on official Macedonian coins which prooves this theory.
Reverse: Wide trident; MAKE / ?ΔONΩN?
Die Orientation: -
Weight: 6.7 g
Celtic imitation of Macedonian issue from 185-168 BC. Overstrike of Thessalonica, 158-31 BC, head of Dionysos with ivy wreath right, goat standing right, ΘEΣΣA_ΛO / N_IK_HΣ, (NE) / ? other monograms, Sear #1466; BMC Macedonia p. 110, 10 - 16. Wave on Strymon's face is relic of original coin also there is slightly visible inscription (perpendicular to trident). Imitations from Serdi region weren't used to fool Macedonian traders but as their own currency. This coin is one of overstrikes on official Macedonian coins which prooves this theory.