The extensive collection of Dr. Kronenberg is not a traditional collection from the perspective of most collectors and / or exhibitors.  Rather it is the reference collection of a high level expert and avid collector.  The viewer must remember the following two facts:

Dr. Kronenberg's collection was created as a reference versus a traditional collection.  As a result both genuine issues and forgeries are illustrated in most Albums of this collection.  This material was never exhibited and therefore was not required to conform to exhibition criteria.  For the collector seeking information on both genuine and forged material, this material is a unique and valuable resource.