Post-WWII West German 'Notopfer Berlin' Taxed Cover

This is a hand-addressed postal cover from West Germany, likely dating to 1951 based on the stamps used. The envelope is made of light tan, fibrous paper with visible vertical and horizontal fold lines. It features two olive-green 10+5 Pfennig 'Helfer der Menschheit' (Helpers of Humanity) stamps depicting Vincent de Paul, issued by the Deutsche Bundespost. Crucially, it includes the small blue 2 Pfennig 'Notopfer Berlin' (Emergency Relief Berlin) tax stamp, which was mandatory for mail in the Western zones (outside Berlin) from 1948 to 1956 to support the blockaded city. The address is written in fluid black cursive ink to 'Herrn Franz Schmitt' in Mainz, Rheinstr. 48. Several circular date stamps (postmarks) are visible but partially obscured. The condition shows age-related toning, minor edge wear, and a distinct vertical fold through the center. The stamps are canceled, indicating the piece has passed through the postal system. This item serves as a significant historical artifact of the Cold War era and the post-war redevelopment of the German postal system.