Your Kennedy is 90% silver and looks nice. I agree with Onedollarbillnut, that is a blank holder your grandfather put those in.
Since you are new, get yourself a pair of cotton gloves, oil from your hands ruin coins, or only pick them up by the rims..
To me the best is to get folders to keep your coin collections in. Stay away from the 'press-in' ones, you want folders that have slides that protect the coins.
Cheaper and quite OK option is to get 2x2 cardboard flips to keep you coins in. You can still look at the coins without worry.
Welcome, a lot of great people here... Most of all, have fun.