Byzantine Coin With Saints

Actually a lovely coin

Well, Justin II and Sophia didn't have a year 21, and it would be strange to have a half follis overstruck on a follis (especially since a Justinian I follis would be huge). Besides, I don't think the style of the double portrait is right for that pair, anyway.

I stand by my previous theory of a Heraclius SB 810 follis, regnal year 21 (631 AD), over an earlier half follis (perhaps of Justinian, for all I can tell, but probably later).

If true, incidentally, it will make this coin eligible for the "walking back by decades" thread

I see what your saying. But here is my thoughts on this coin. The coin was overstruck on an earlier example of a follis, we agree on that. But what I think has happened, is what you are saying is XXI has actually been altered to ANN (O missing) and if you look to the right of the K there is an X which would make it year 8 of Justin II reign 574/75 AD. This is one of those iffy coins.

Come to think of it - what the weight is?

If it's ~10-12 grams, it's a SB 810 of year 21, just like I said originally. (Apparently due to a brief reform the coins of this particular year are heavier than usual for the type.)
If it's ~5-7 grams, it's a SB 812. If it's ~3-4 grams, it's a SB 1010 (not ruling it out).
If it's somewhere not in those ranges... could be anything really (even Justin II, though I still think the portraits don't match that).

BTW, I think there's another X next to that X right of the big K, so (assuming it's not part of the other strike's mintmark, which it might well be if we're looking at a 3/4 follis) the year would have to be over 20, which pretty much only leaves Justinian I and later Heraclius.
A Heraclius half follis of the late 630s would be way too small for this (well under 5 grams); a late Justinian I half follis from the 550s would indeed be about the right weight to be restruck as a year 21 Heraclius follis or 3/4 follis, however. (It would have to be 70-odd years old by then, mind you, but this isn't beyond plausibility.)
[EDIT: on second thought, arnoldoe's pics made it clear that the undertype, whoever it is, is not Justinian but another double portrait - not sure if Justin II or Heraclius is more likely. Curiouser and curiouser.]

For what it's worth, WEGM shows a very nice example of 3/4 follis of Heraclius from year 21, which is indeed a good match for this coin. Apparently a rarer date too!

The best part is, if it goes the way I (and arnoldoe) think it does, this coin would be eligible to advance the "walking back by decades" thread (year 21 of Heraclius = 630/31 AD).

Wow interesting stories! I have here the weight. it is 6,26 grams and the diameter aproxximatly 24mm
I am not an expert in this period. Just my 6th coin from byzantine period.

With that size and weight It would make it a Heraclius, I stand corrected.

Its probably a sear 815 over the 3/4 follis,
sear 815 has dates from year 20-31