This looks like the 2004P BU Set - standard 7 coins issued @ 23.95 (oh-canada set). Over 53,000 sets were minted.
Unlikely that anyone removed the coins for the purpose of toning. There would also be major evidence. In your set it appears the plastic is intact.
The other possibility is a forgery using regular circulation coins, but the coins look about right for this set.
The possibility of some sort of chemical reaction but I have not seen anything like this on any of similar sets I've had. I am not a chemist so I don't know what could cause this (sun exposure?).
Unlikely that anyone removed the coins for the purpose of toning. There would also be major evidence. In your set it appears the plastic is intact.
The other possibility is a forgery using regular circulation coins, but the coins look about right for this set.
The possibility of some sort of chemical reaction but I have not seen anything like this on any of similar sets I've had. I am not a chemist so I don't know what could cause this (sun exposure?).

























