Byzantine 780-91 Irene and Constantine VI ???

I know nothing about Byzantine coins, but recently purchased a beautiful and very inexpensive coin listed as “Justin 1 Constantinopolis 522-527 BZ05”.   It appears to me that the listed identification is incorrect.   Could it be identified as  an Irene and Constantine VI 780-791 AE 21.8?? The coins diameter is 22 mm and it weighs 4.22 g.  If it was very inexpensive, is it likely a fake?    

You're right, Constantine VI and Irene looks like a better match. You can find a couple of close ones here: https://www.zeno.ru/showgallery.php?cat=4243

I don't think it's fake, it's just quite worn. Probably the seller just wanted to get rid of it.

Thanks!