I found a bank web page (in english https://www.piraeusbank.gr/en/idiwtes/ependyseis/agora-polis...) with more info about buying gold sovereigs. A gold sovereign is sold by the bank at 480 euros (https://www.piraeusbank.gr/en/Idiwtes/Epitokia-Deltia-Timon/...)

This is very popular here because gold sovereigns here in greece are traditionally given as presents from close relatives on very important moments like marriage, child birth etc (i.e when a child is born its grandparents will give a gold sovereign to its parents)