25 Cents - Elizabeth II Confederation- 50%

Canada's centennial coinage program was planned years in advance, with sculptor Alex Colville commissioned to design all seven denominations. The 25-cent piece was originally struck in 80% silver, but a sharp rise in silver prices mid-year forced the Royal Canadian Mint to quietly reduce the alloy to 50% partway through 1967's production run — making KM#68a a mid-year substitution rather than a planned issue.

The two alloys are visually indistinguishable in hand. Specific gravity testing or XRF analysis remains the only reliable method for separating them without reference to die characteristics.