A Collar Die clash, aka rail road rim on reeded coins, is when the die partly strikes the top edge of the collar die. This indents that area of the die so when it strikes a coin it imparts what appears to be a “doubled” rim.
Almost.. It's a simple Misaligned Die Strike. The collar rose up a bit due to a high pressure strike and caused a finned rim. It has since folded over on itself. And.. It would be a Double rim not a Doubled rim in this case.
