Country date denomination ? Cob? 20mm diameter

1

gives me more a feeling of Hungary, Poland....

MA or VIII  ?

V111 must be 8

could this be a Spanish counter mark of a byzantine coin?

It should be this one : https://en.numista.com/catalogue/pieces89614.html

However we need the weight of your coin to determine the host coin and the value of the last strike... I assume there are some wrong informations on the numista page as it doesn't seem coherent (there is an anachronism for the value of the coin : the 8 maravedis countermark is previous to the 1658 strike).
The weight of your coin could confirm my assumptions.

For me the host is probably a 8 maravedis minted between 1602 and 1626 :
https://en.numista.com/catalogue/pieces24099.html
https://en.numista.com/catalogue/pieces40685.html

This coin was countermarked for the first time in 1641 or 1642 with the "VIII" countermark and the year on the other side to confirm its value (some other coins were reevaluated during this period)  : https://en.numista.com/catalogue/pieces68083.html

After that, the coin was devaluated to a value of 4 maravedis in 1658 or 1659 by striking the crowned RX on one side (first picture) and the crowned "PHILIPPVS" monogram on the other side.

Normally this coin should have a value of 4 maravedis (I'm almost sure about that).