Olynthos, Macedonia. Chalkidian League. ca 432-348 BC. AR Tetrobol, 14 mm, 2.44 g. 

Laureate head of Apollo left, Delta behind neck. 
X-A-L-KID-EWN around lyre with five strings; all within incuse square. 

Sear SG 1425; BMC 15-18; Robinson and Clement group C, 22

Sold by Nomos AG - Auction 16, Lot 63, May 2018.
Estimate: 300 CHF.