Leave it that way! Mine had been flat for 23 years until I just opened it to image the text. It obviously didn't like being disturbed.
So was mine, sandwiched between two lengths of cardboard and in the original box. It is now back together like that.
I bought mine in an LCS when I lived in Washington State near the Canadian border. Cost me a whopping $12.95. I still have the receipt for it. Lol
Nice! I collect the nickel coins from Canada, so both the 1999 and 2000 sets are on my list (circulation coins only), but so far I just have a couple that I got from circulation while traveling. But I expect to get to them soon enough. The RCM does go overboard with the varieties, so I am kind of happy that since nickel coins have been discontinued that I don't have to keep up. But I'll get these sometime.