Nice score just from an antique shop. When I go to the few rare shows in my area Commemorative coins often come with a COA, Certificate of Authenticity. Canadian RCM commemoratives have been either 92.5%, 50% silver and Nickel Steel and always issued a COA. Bullion coins will always have a 0.999+FS somewhere. If not, then I resort to some kind of test (I'd carry a Neodymium rare earth magnet or a regular magnet) especially Nickel clad steel coins. There are various tests if the dealer cannot help you but it always pays to do a little research first.