Port quarantine station ship (Japan)

(1) The current flag of Japanese quarantine is a yellow over blue bi-color flag and blue "Q" on upper hoist. The flag was adopted 16 June 1954. The yellow is an international color for quarantine and blue stands for sea and sky. "Q" is of course the initial for quarantine.

(2) Between 16 June 1954 and 8 April 1948: The white flag with yellow large "Q" was used but the white flag was hard to distinguish on the sea.

(3) Between 8 April 1948 and 1 August 1921: The blue over yellow (not yellow over blue) bi-color flag was used. The flag did not have a "Q".

(4) From 1 August 1921 and April 1902: As quarantine vessel flag, the Harbor master flag was used. The flag was red "H" of harbor master on white background.

(5) Between April 1902 and Jull 1879: The plain yellow flag was used as the first quarantine flag in Japan.

source: 'History of quarantine system in Japan' issued by Ministry of Public Welfare.
Nozomi Kariyasu, 15 April 2000