Canada 25 cents 1912-1926

I have a very worn Canadian quarter, on which the date is not readable. Is there any way to distinguish these two types other than by the date? Obviously it is only worth bullion value but it would be nice to know which type to list it under.

https://en.numista.com/catalogue/pieces373.html
https://en.numista.com/catalogue/pieces372.html

If you have good hearing and one of each type, you could ping them off a desk and hear the tone the silver makes. But with .925 and .800 the difference is small so it's tougher, .8 vs .5 (like for the 67 coins) is much easier.

Shouldn't there be at least a small difference in dimensions (weight, thickness or diameter) if it's made of a different alloy?
On the coinpage on numista at least weight and diameter seem to be identical ... must be thickness then? Or error in weight?

if they are so worn you cannot read the date, the difference in weight due to different alloy will be less than the difference due to uneven wear.

edit to add, I just did a little figure. assuming the alloying element is copper - 80% silver is 2.2% lighter than 95% silver. for a canadian quarter that would be about 0.12g . Evidently the thickness did change to maintain the constant weight spec.