The wine is Mount Eden Vineyards Santa Cruz Mountains Chardonnay 1990, estate bottled, bottle #06523, 13.2% alcohol. The wine was stored properly since release, the fill was very high, and the cork was very sound.
The color is light yellow. The wine is holding well, with no oxidation, and likely will keep well for at least a few more years. The general structure of the wine is about as close as you likely are to come to an excellent Puligny Montrachet in California. The wine is now perfectly balanced with ample, clean acidity and great complexity of fruit - you may get hints of citrus, apple, minerals, wild flowers, etc., but it is difficult to say exactly what. The finish is long. There is now a bit of creamy character. The oak is well under control. The alcohol level is not excessive. Unfortunately, this was my last bottle.
When everything is right, Mt. Eden Estate can be the top Chardonnay in California. It can be rather harsh when young, and the best examples require many years to come around, but then so do many top white Burgundy wines. It is one of the few California wines that often improve for many years, can hold over 10 years, and often much more. However it has varied quite a bit over the years. There have been changes in ownership and wine makers which sometimes have made a difference. On the average, the top reserve wines of Au Bon Climat are a safer buy. However, when everything is right, Mt. Eden Reserve is more Burgundy like and perhaps can even outlast Au Bon Climat, which often ages well for 10 years or more. If one is looking for instant gratification, neither mentioned wine likely is the first choice. However, if you are willing to properly store the wine for several to many years, it often will outclass nearly all other Chardonnays made in the US.