An article by W. George Schmid in The Hosta Journal (1985 Vol. 16) discusses the University of Munich's trial gardens named Staudensichtungsgarten Weihenstephan, "...a fine collection of hostas. These are of great importance from a historical standpoint, because many of the cultivars there came from the early German hybridizers, including Georg Ahrends . They include H. sieboldii (syn. H. albomarginata) 'Alba Improved', H. ventricosa 'Superba', H. tardiflora  'Hybrids' and H. 'Elegans'."

We would suspect that this is a sport of Hosta sieboldii 'Alba' but...we don't know for sure.