Canadian 50% ....... Why couldn't they make this simpler?

Help me understand how coinflation lists cut off years for 90% & canadian 50% coins.

I just got done sorting a can full of old & foreign coins. I was concentrating on finding some silver. As I was referring to coinflation for cut off years, I became confused. I guess it's never easy.
for instance:
Coinflation shows USA 90% like this: 1946-1964 Roosevelt Dime
That means every dime from 1946 through all of 1964 is 90% silver.
Ok cool. This also works for quarters & Halves.

Now pennies.
Coinflation shows: 1909 - 1982 Copper Lincoln Cent Value .026 cents.
Simple yes?
Wait... aren't some 1982 pennies copper & some 1982 pennies zinc.
So really it should be shown as 1909 through 1981 95% copper.
1982 coins have to be weighed.
correct? (3.1 grams vs. 2.5 grams)
Those of you that machine sort, don't have to worry, must be nice!

Now about Canadian 50% silver, I ran into a similar issue.
Coinflation shows:
1920-1967 Quarter $0.25 $4.3019
1967-1968 Quarter (50% silver) *** $0.25 $2.6887

So does this mean that all 1920 through all 1966 quarters are 90%?
and
Just some 1967 through 1968 quarters are 50% silver.

Anyway, I found one 1967 quarter that weighs 5.9 grams.
I think it's 50% yes?
But the 1968 I found could be either 50% silver or all nickel according to Wiki, and the weights are supposed to be the same.
How can I tell the difference??
(the 67 sounds silver the 68 sounds dull)