Yes, as you can estimate from the Hodegetria on the
obv., the blank used was much too small for the die of the
boulloterion. But you are very lucky that we can read the family name Anzas on the last line: [T]W ANZA. I don't have time right now, but if you are even luckier, this seal is published and you will know the personal name as well. I think I can read traces of Hypatos and [K]PIT TU R(elou), judge of the Velon as well. I'll have a look eventually, but maybe you can find something. Date would be 2nd half 11th century.
Regards
Gert