I usually drink the beer I make within a few months, but I once made a batch where I saved several bottles for around a year. The aging produces a better tasting beer, like the aging of wine.
Beer has a lower alcohol volume than wine typically, so understandably one might wonder how it could still be good 86 years later. If I had a bottle of such beer, here's how I would know if it was still good:
1) There is still pressure when opening the bottle. Part of the preservation of beer comes from the fact that it's carbonated (naturally with yeast and sugar or artificially in commercially made). The layer of CO2 protects the liquid from oxidation. So if it's still carbonated, that's a good indication.
2) The smell. Oxidized beer has a horrible smell. It would put anyone off before coming close to their mouth for consumption. If it still smells just like beer and not some nasty fungus/mold it is very likely to have been preserved.
