2011 Washington State D Quarter Possibly Struck On Canadian Planchet?

Specific gravity measures the density of the coin. It requires a digital scale with at least two decimal places of accuracy, a plastic cup, water, and dental floss. (Yes, indeed. Bear with me.)

1. Zero the scale.
2. Weigh the coin when it is dry. This number will become the numerator in the fraction.
3. Fill the cup with enough water so that the coin can be covered standing up, when it is suspended in the water.
4. Tie the dental floss around the coin so that the coin won't slip out of the loop of the floss. Leave enough floss so you can dangle the coin in the water, fully submerged but not touching the sides or bottom.
5. Place the plastic cup with water on the scale.
6. Zero the scale. (This is essential)
7. Dangle the coin in the water, submerged, not touching the sides or bottom of the cup. The measurement will become the denominator of the fraction.

The rest is math: the dry weight (numerator) divided by the submerged measurement (denominator) = specific gravity of the coin.

Specific gravity does not depend on the size or denomination of the coin. It measures the relative density of the composition. If my arithmetic is correct, specific gravity of any copper-nickel clad US coin should be very close to 8.92.