1950's Air Mail from Finland to West Germany

Air mail letter Helsinki -> Köln, West Germany 18.11.1953. 2nd weight class letter (21g-40g, valid 1.1.1953-31.5.1956) 40 marks. Air mail surcharge 3 marks/5g (24.10.1945-30.9.1957). The attached stamps match (55 marks) an air mail letter rate for a letter weighing 21g-25g. No arrival post stamping.

Air mail greeting postcard Helsinki -> Duisburg, West Germany 17.12.1952. The postal fee has been paid by a single 15 marks stamp. The 15 marks does exactly match the postcard rate of the period but then there is the missing air mail surcharge. Air mail surcharge 5 marks/5g. It was possibly to send greeting cards using a cheaper rate as printed matter (more on this here). The printed matter rate was 10 marks (<50g, 1.1.1952-31.7.1958). The 15 marks would be enough to cover the printed matter and air mail surcharge but would still be 2 marks overpaid. Nevertheless, the 15 marks M1930 stamp alone on a postcard abroad at that time period is still a rare occurrence. 

Air mail letter Helsinki -> Hamburg, West Germany 25.11.1950. The combined face value of the attached stamps on the cover is 59 marks which does not match any possible combination of letter and air mail surcharge regardless of weight. As the stamps are all from the same Red Cross series published in 1949, it is safe to assume that the sender has overpaid for philatelic purposes only.

Air mail postcard Helsinki -> Duisburg, West Germany 7.7.1953. Postcard rate (1.1.1952-31.5.1956) 15 marks. Air mail surcharge 3 marks/5g (1.12.1948-30.9.1957). Correct rate.