I received a (un-opened, seal-intact) bottle of 100 proof Old Grand-Dad with 2 dates upon the seal... Fall 1959 and a little lower Fall 1964... for my birthday. Is boubon this old still drinkable? Does it get "better" with age? Is it valuable as such? It sure looks good... but should I crack it open?!? Thanks in advance for any information you can give me!