5 Mark black overprint as a single franking on window envelope with first day cancel "Berlin SW 11 bc 6. 9. 48", faultless condition, certificate with photograph A. Schlegel BPP (2011) : "it is me only this a document with the value to 5 DM black overprint with first day cancel recorded. ", Berlin rarity, provenance collection Srkala! The cover was at the 7. 9. 2011 by Schlegel for 15. 500 EUR percentage of bid price and so on. Auctioned, see Michel special 2014 on page 708 !