From 2001 to 2006, most 1¢, 5¢, 10¢, 25¢, and 50¢ coins issued for circulation were struck with a P Mint Mark to represent the Royal Canadian Mint's plating process.
It is a commemorative, but is extremely common. Just exchange value. A proof will have a mirror finish, and I believe the nickel is silver in their proof set, unlike in our proof sets.
It is rare for a coin to say it's a proof when it is. P is usually a mintmark, or a metal designator. However, Belize made their silver proofs, and stamped "Silver proof" on the edge.