Wow. That is all.
The coins alone are probably worth a fair chunk o'change.
Not reporting it is the most illegal thing you can do. It's also the smartest!!!! Like you said, it's amazing how Uncle Sam loves to take his cut out of a pie that he's already had a cut out of.
If the Sheriff or county Constable seizes that money it is GONE. It's all in the safe...best place for it.
Best that you and your Dad found it. Think what would happen if God forbid your Grandpa passed on and some movers or somebody just stumbled across it. You'd never know it was there, they sure as hell wouldn't say anyting...at least your family will get to split it up down the road.
If Grandpa is in bad enough shape to be in a nursing home, he can't handle his own finances. I speak from experience because MY father is in a nursing home, waiting to die. Five years ago, my mom, my brother and I decided to have the papers drawn up to have all decisions concerning Dad's finances and healthcare removed from him and transferred solely to Mom...and my brother and I should somethig happen to Mom.