Good luck. Chances are it's still good, if it was stored properly. Can looks immaculate though. The can has got to be worth something. It's actually a cool piece of history. It is collectible, I'm sure..
I just finished up a batch of 231 that was opened in 1963. I picked up the 2/3rds full commercial 50 pound can back in 1977. I've used it for my .45ACP bullseye softball load since then. It shoots the same today as back when I first worked up the load. Storage is the key.
If it smells good (not acrid) and is not showing red dusting and if it freely flows (not clumpy) it will be fine.
I use very old H4831 a lot. It works great with no issues that I've ever run into. If that powder was stored right, it'll go bang every time. Fantastic powder. Mine is old WWII era powder that I bought for $5/lbs.