We would like to thank the University of Greifswald for a permission to display scans from their map collections via Mapster. We have currently added:
358 scans of Soviet maps, scale 1:100,000, from 1930s and 1940s,
and
25 sheets of a 1:1 M map in the International Map of the World system
All maps are available as 300 dpi scans. 
Please note: index sheet for the 1:100,000 maps covers a large section of Europe, so it takes a long time to load!
By the end of the year we should have added  a few dozen maps to the above map sets, this time from a private collection. Early next year we plan to populate the index sheet of the Soviet 1:50,000 map with approx. 900 scans from Greifswald, and add about 50 more sheets from private collection.