The OSTROPA Souvenir Sheet was issued on 23 June 1935 to commemorate the Eastern Europe Stamp Exhibition (“OSTROPA”) in Königsberg, 23 June – 3 July 1935.
The four stamps depict:
The purchase price was 1.70 M.
This issue is difficult to find in great condition, as the original gum was very acidic, and if not removed, would degrade the sheet at a much faster rate than normal. Those which had the gum removed soon after issue tend to have whiter paper. The acid in the gum turned the paper brown over time.