Old bottles of Jack Daniels

I need some advice from experts. I was cleaning my mother's basement last night, and came across some stuff from my father's liquor cabinet that had been stashed. Included were two bottles of Jack Daniels that were purchased some time before 1975. They are both square bottles with green labels holding 90 proof JD Old No. 7. The labels and seals are pretty water-damaged, but intact and readable.

Are these worth anything (that is, should I try to make a mint on eBay)? Or should I just crack one open and have a drink?