The wine is Monterey Peninsula Winery 1976 Amador Zinfandel, Ferrero Ranch, Late Harvest (dry). It contains 15.5% alcohol with residual sugar of only 0.2%. The bottle was properly stored since release, and there were no cork or other issues.
There were many Zinfandels and other red monsters made in California in the 1970s. Some of the wines of David Bruce come to mind. However this wine is the most extreme that I can recall. Many monsters such as this are undrinkable when young having extreme excess of tannins. This wine, even at 10 years, was about as good as a very green persimmon. However the wine is now ready to drink. It still has considerable fruit and is dry enough to serve with stronger red meats including game. It is a quite decent wine although a bit overblown for my taste. There is still considerable tannin, but not excessive. The color is still quite dark with only mild evidence of age around the rim. There is still plenty of dark fruit character in the bouquet and taste.
Some information from the back label is interesting. The wine is said to be the biggest and most intense Zinfandel the winery had ever produced. The grapes were picked at 28% sugar by weight. 1976 was a very dry year. The grapes were very small, almost the size of currants. The wine was aged in old neutral oak cask, since the last thing it needed was more tannin from oak. It was said that the wine needed age. One could drink it early as a learning experience.