It is a so-called "anonymous follis" which is said to be minted in or around the reign of Romanus IV Diogenes (1068-1071) in Eastern Roman/Byzantine Empire.
The OP reverse needs rotated 90 degrees to the left. Even without the emperor's name (as correctly supplied by @Herberto) this type stands out enough to make it a relatively easy attribution. https://www.wildwinds.com/coins/sb/i.html Here is mine:
