Korea's  Taegeukgi  Flag
Early versions of the Republic of
Korea's Taegeuk-gi National Flag
said to be from 1882
1912,  Cheongsong County relic
Taegeukgi that hung in the office of Kim Gu, President of the ROK in exile in China, about 1940-45.
Note the vertical orientation of the Taegeuk -- more Chinese-style.
It was designed to display loyalty to the ancient oriental (Chinese-origin) spiritual
culture(s),  in opposition to Japan's late-19th-cen abandonment of it in favor of
"barbaric" westernization.  It features a Koreanized version of the
[Chinese Daoism's Taiji, Grand Ultimate or yin-yang symbol], and four out of
Palgwae [Bagua, the eight Trigrams of the I Ching], the ones representing
Heaven, Earth, Fire & Water,  whose three-level structure represents
[Heaven, Earth & Humanity],  the fundamental oriental Trinity.
"The world's most philosophical flag"
the above flag rendered backwards, in
an 1882-7 US Navy Signals Handbook
1882-09 version, attributed
to activist Park Yeong-hyo
Late Joseon Dynasty and "Daehan Empire" versions
both from 1883 Qing Dynasty diplomatic records
-- note the dots in the maximums of the swirls --
Korean flag given to US diplomat Owen Denny by King Gojong in 1890,
in US Navy Museum, Annapolis, Maryland.
detail of a U.S. postal stamp at the end of World War II
Joseon Dynasty flag used around 1800,
with all 8
Palgwae Trigrams, in the Earlier Heaven arrangement
1910 "Daehan Empire" version
treasured Taegeukgi used by
resistance fighters in 1911-12,
kept in Samgak-san Jingwan-sa.
the modern Taegeukgi national flag of the Republic of Korea
see the Wikipedia article about it
a crude version dated to 1885, in the Seoul Museum of History -- first vertical-divided
two-fat-parts version, and unique that the left half is is white instead of blue or yellow.