You could try www.cdnpapermoney.com
I think they have forums. who you would be able to ask.
We have some money collectors on here, but none have replied yet.
Personally I am not sure if an old $50 bill would be collectable.
It definately would be if it had any kind of serial number that would be collectable on todays money such as Radar, (1234321) or ladder ( 12345467 ) declining ladder (9876543)
low or high number.. low is under 1000
or even repeating number such as 1111111
even the million notes are rare 4000000.
Other than that .. asking on their forums might be the best bet..
If you wait another 50 years it would probably be collectable.