Michael Ducas AE follis, with strange countermark, or probably overstruck [решено]

I found quite interesting follis with big countermark or maybe overstruck.
I believe it's M. Ducas follis.
But I have a question - what is over it ????

That coin is usually overstruck with earlier follis, so I suspect that is what it is. For instance:

Byzantine Empire: Michael VII Ducas (1071-1078) Æ Follis, Constantinople (Sear-1878; DOC-14b)

Obv: Bust of Christ Pantokrator facing, bearded, with cross behind, wearing tunic and himation; right hand raised before breast in blessing, left hand holds book from beneath. In field, IC and XC above lateral arms of cross; six-pointed stars beneath them to left and right
Rev: +MIX AHΛ RACIOΔ; Crowned bust of Michael facing, bearded, wearing modified loros with collar-piece and crown with cross and pendilia, holding in right hand labarum, in left globus cruciger

Overstruck on a follis of Romanus IV (Sear-1866), next coin is NOT mine

wow! Thank YOu very much !!! how important to know a history of each coin !

respect !

best
D