The Grecos have two serial formats.
The Greco/Ibanez serial format is MYYXXXX with M=month letter(A=Jan...L=Dec), YY = year, and XXXX = production number.
The other Greco serial format is YXXXX with Y = year with no decade info, and XXXX = production number. This serial can also be a MYXXXX format which is the same as the YXXXX format but has a month letter as well.