As of now, the Old Masters collection of the Gemäldegalerie Kassel is searchable online. Still being a work in progress, the database will be updated reguarly. The digital database offers detailed information on the rich collection of paintings in the museum. It uses the Museums collection catalog, published in 1996 by Bernhard Schnackenburg, which has been sold out for some time.

The database (for now only in German) can be found at:
http://altemeister.museum-kassel.de/