Modern COPY of an ancient Greek coin (stater) from Aegina

Modern COPY of an ancient Greek coin (stater) from Aegina as follows:
Obverse: Turtle with 5 pellets on shell
Reverse: Incuse square divided into 8 parts
21mm diameter, appears to be made from good quality silver, 12.39gm.
Purchased in Athens more than 20 years ago.