@mrv, I'm no expert in Byzantine coins, but I am quite sure that this is what you have here. The denomination is that big letter M on the rev (40 Nummi). ANNO stands for year, but the right side of the flan is too ragged to make out which regnal year--maybe 6? Also, the CON in the exergue means that it was minted at Constantinople.
Your first picture is upside down I believe, but I can make out a few key letters (d M TIB P).
I'm hoping someone with more knowledge will weigh in, but Tiberius II Constantine from the 6th Century seems to be a likely ruler (especially Sear #430). Here is a link to a clearer coin for comparison with yours:
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