Size Chart

 cm -------Uk------- US

54 -- 6 5/8 -- 6 3/4

55 -- 6 3/4 -- 6 7/8

56 -- 6 7/8 --    7

57 --     7    -- 7 1/8

58 -- 7 1/8 -- 7 1/4

59 -- 7 1/4 -- 7 3/8

60 -- 7 3/8 -- 7 1/2

Date Code

K 1968
Z 1969
M 1970
X 1971
B 1972
L 1973 (1987)
O 1974
S 1975
R 1976
A 1977
U 1978
F 1979
E 1980
G 1981
I 1982
C 1983
H 1984
T 1985
P 1986
L 1987 (1973)
Y 1988
N 1989
D 1990

Reichsbahn faehr schiffahrt-DDR State Railway Ferry. 
Two piece hat, white fabric top. The band, visor, cap cord and buttons of hat same as used in the navy petty officers hat. Embroidered cockade. Size 54, no date. If you have any images or information on this hat please share it with me
Interflug-Internationaler Flug-(International Flight)-DDR State Airlines.
Blue fabric crown and visor, embroidered wreath and metal cockade. Gold cap cord, bronze/brown pebbled buttons. Owner's initials U.S . Size 55. VEB Mutzenfabrikation Berlin.