Hi, Kath. The
monogram reads ΘEOTOKE BOEΘIE - Theotoke Boethei. It is an invocation of the Virgin, meaning literally `God-bearer, stand by (
help)...´. On the
reverse I can make out the name ΔHMITPIῳ (Demetrios), along with titles, one of which might be XAPT... (chartoularios, an administrative position). This is probably from the early to middle
Byzantine period 7th to 9th century CE. I am sorry I don't have more for you but I will keep looking. I agree with Djmacdo, "
seals and
tesserae" post will likely get more
help.
Regards, Jimi