Those coins was 80% silver with bonded 21.5% silver and 78.5% copper. Normally this bonded must not detached. It is a very unique and rare thing to happened. Me I try to look for reasons but do not come out in my mind. The bonded silver normally will make mass with core. Very strange effect here.
I hope everyone understand that I try to see what could cause this. the coin her self is unique I see like this. small scale yes , but so large effect? NO.
Only a structural analysis can tell us the causes, Sorry I am crazy for the reasons.
for me it is unique.