Yup absolutely Byzantine. The coin is called a solidus. They replaced the older Roman gold aureus. I have one myself. One thing I love about them is that they are as pure gold as was possible to refine back then. I believe around 96% pure gold. Or 23K. If you’re asking about value like in your other post it’s hard to tell without closer examination (better pictures of both sides of all the coins) but I can say that if they are real you should be able to get at least $300-400 for each of them and potentially more depending on which Emperor minted each.
The top picture shows the reverses. The emperor's name is on the obverse. The one obverse that you sent is of a coin of the emperor Maurice Tiberius, who reigned from 582-602 A.D., so the coin dates from that time.
