Tang-soo-do does not use the traditional Korean black belt in its ranking system. Kee believed that persons who wear a black belt believe that they are masters. Since the martial arts are a continual learning process, he felt that no one can ever truly become a master. Therefore, Tang-soo-do dans wear a dark blue belt.
When the Moo Duk Kwan had rank testings the Chung Do Kwan's Lee Won Kuk and Song Moo Kwan's Ro Byung Jik visited and built a good friendship, but regarding dan certificates and promotions, they had disagreements with Hwang Kee.
The first Moo Duk Kwan dan holders were Kim Woon Chang, Hong Chong Soo, Choi Hui Suk, Yoo Kwa Young, Nam Sam Hyun, Kim In Suk, Lee Bok Sung, Hwang Jin Tae, Won Yong Bup, Chung Chang Young, and Lee Kang Ik.