Local registered letter with perfin “DDR” in the stamp. The letter is franked correctly with 40 øre, 10 øre was the rate for local letter from March 1st 1921 to June 30th 1946 and the rate for registering was 30 øre from July 1st 1940 to April 30th 1951. The stamp is cancelled July 5th 1943 with København 3. nr. 23a København 3.2 Bro Vd-1
Note the violet oval arrival stamp on the back.