This larger flan type is one of the rarer issues for this series, to be sure. Here's my thread for this coin: https://www.cointalk.com/threads/a-nice-rare-follis-of-constantine-iv.361222/
Another fun group of Justinian folles are his plague year coins from Constantinople. He survived of course, yet the progression of his condition and recovery are quite revealing.
My first follis was this rather miserable looking one of Constans II strangely enough, in some angles it almost looks silvered, but I know that would not have been the case.