Michelin xwx whitewall tire

[CarlG]

I just got 5 new tires on my car but kept the spare which appears as if it has never been on the road. It must be at least 25 years old but has always been in the trunk in the cover so it has no sun aging. I know they say you should not use a tire that is over 6 or 7 years old which is why I decided to replace it. I kept it as I wonder if it has a value to someone who has a show car. Should I try to sell it on EBAY, and if so, what might it be worth? Thanks for your ideas.