Ok. the excise stamp states 1977 but it would not be that old. As to quality? Well air in the bottle may give it an off taste. If it is cloudy or clumpy DONT drink it!!!! If its clear it could be ok. Your local nearby distillery have labs for quality control. If you know someone or perhaps it would be for good practice take it to them to test. I'd be interested in the results.
But when in doubt dont! I'd trust a sealed bottle anyday.
If it turns out good let me know.