DDR B144 - Surtax for North Viet Nam

This East German semi-postal (a stamp with a surcharge which is given to a cause or charity - like the US breast cancer stamp) in support of the people of Nort Viet Nam. I am absolutely smitten with the image, so clean, minimal, and simple yet so powerful (tattoo?) and I am blown away by the inscription, not translated in the Scott Catalog - efforts to translate "unbesiegbares" online come up with the term "invincible." And FYI - the spots on the image are on the stamp, not due to sloppy scanning by your host : ) (10/25/66)