The Chablis Grand Cru - Les Preuses 1979, Rene Dauvissat, was my last bottle, and has been properly stored since release. The fill was still high, and the cork was sound.
The color is light yellow with a hint of green, what would be expected for a Grand Cru Chablis in good condition. There was not a trace of oxidation. There was good fruit of a complex mixed citrus character, as well as some flinty mineral character. There is enough, but not excessive, acidity. The wine is now more rounded and complex than when young.
It is not at all unusual for a top Chablis Grand Cru to last this well. I have read several accounts of visiting VIPs being offered samples of old top Grand Cru Chablis by growers at their cellars, and the wine was still holding very well at several decades of age. In fact a Grand Cru Chablis, at the best, is a rather big wine, often has high alcohol, but still has plenty of acid and some flinty character. It can be of about the weight of a top Puligny-Montrachet, although of different style. It is big enough to hold up to about the same dishes as will a Puligny-Montrachet. I say serve a lesser wine or lemon juice with the raw oysters, and save a top Grand Cru Chablis for the main course. I have yet to have a Grand Cru Chablis of top repute and good vintage year that showed any oxidation before 10 years if properly stored and having a good cork. I can not say the same for some Puligny-Montrachet of good reputation, especially in very hot years when acid is low.