Per the winery:
1990 Ockfener Bockstein Riesling Auslese
Residual Sugar:58,1g/l Acidity:10,5g/l Alcohol: 8.5% by vol.
Article describing a tasting with the producer.
http://www.winerambler.net/blog/sultans-sweet-learning-about-matching-residual-sugar-mosel-riesling-food