Thank you for your comments.
I thought about a die flaw first to, since, on my coin the interesting
area is damaged, too and I was not too sure. Since I have found the
Lanz coin, I am sure it must be an engraver's error, since the I is to much regular and similar to the other I's. On the other hand, the dot on the right
side is much nearer the last I than on the left
side and the gap would rather fit to the third I.
Still, given the overall apperance of the letter, I am
still conviced that it reads IIII, whilst it is an engraver's error for sure and it should obtain but a footnote in the scholarly works.
Semper
paxhelcaraxe