this is what TT means:
from
http://www.lghk.org/en/history/founders.htm
however, i have never heard in our gungfu family there is any connection of the tiger crane logo and the Hung Mun "logo"
the history info i have heard: Lam Saiwing's school logo was a circle with the Chinese characters "Lam Gwun" (Lam's [Martial Arts] Gym):
from
http://www.lghk.org/en/history/index.htm
when Grandmaster Lam Jou, nephew of Lam Saiwing, took over both branch schools and later also the main school, he has changed the name of the school/association and also the logo. it is called
fu hok jeung, and actually it is not a diamond but olive. it was designed by Leung Winghaang, Lam Jou's classmate and sworn brother. see bellow:
sidenote: interesting, Lo Man kam, nephew of Yip Man, has similar logo:
from
http://www.lomankamwingchun.com/
i also like the Naam kyun logo by Klaas P. Evenboer (upper part of the image):
from
http://www.hungkuen.nl/