1968 Canadian Quarters

1968 quarters only came in nickel (pure) and .500 fine silver (the rest copper). A magnet will stick to nickel coins. Black tarnished coins are silver. The sound gives it away too - silver is "pingy".

Canadian coins did not use .900 fine or .400 fine. It went .925, then .800, and finally .500 fine.

The reason for these purities was to deter people from melting currency to make jewelry. In Britain, the standard for coinage was .925, and .950 for jewelry. In the States, the coinage was .900 and .925 sterling for jewelry. This forced the public to buy from jewelers, and it forced the jewelers to buy bullion to create their own alloy which was "spot-checked" by assayers by surprise like an audit so that nobody got cheated. This is still done today except that there's no circulating coinage with precious metals. Why did different countries have higher standards in purity? It was like an exchange rate denoted in precious metals. Each country minted their exchange rate in the form of their own alloy and size of their coin to whatever met the demand and convenience of the people and it all got moved around as peoples' whims and fancies changed.

A magnet will suffice, yes.

The 1967 10c and 25c may be 50% or 80% silver but those are the only ones where the silver content changed during the year. There's an old thread around here somewhere with a link to a video proposing a method of determining which are which by analyzing the sound made when they're dropped but most people just accept them as 65% as the mintages are roughly equal.