SK Gas Cup
The SK Gas Cup (Korean: SK가스배) "features two leagues with 5 players each. The winners of both leagues play a best of three match to decide the winner of the tournament. Time limit is 3 hours each." (source: Gobase)
Previous name was New Stars Best Ten. As the name implies, the tournament is for new professionals. The tournament was discontinued from 2009.
According to Wikipedia, the competitors had to be under 25 and below 5 dan. In comparison, the Shinjin O was originally U-30, U-7p and in 2006 also become U-25 (remaining U-7p). The winner's prize of the SK Gas Cup was 10,000,000 won ($8,500).
Previous winners (and defeated finalists):
12nd 2008 Kim Kiyoung (d. Park Jung Hwan 2-1) 11st 2007 Yun Junsang (d. Heo Yeongho 2-1) 10th 2006 Baek Hongsuk (d. Lee Yeongkyu 2-0) 9th 2005 Kang Dongyun (d. Ko Geuntae 2-0) 8th 2004 Park Jungsang (d. An Younggil 2-1) 7th 2003 Cho Hanseung (d. Paek Tae-hyeon 2-0) 6th 2002 Yi Se-tol (d. Paek Tae-hyeon 2-0) 5th 2001 Kang Chi-seong (d. Paek Tae-hyeon 2-0) 4th 2000 Yi Sang-hun (d. Yi Se-tol 2-1) 3rd 1999 Mok Chin-seok (d. Weon Seong-chin 2-0) 2nd 1998 Yi Seong-chae (d. Mok Chin-seok 1-0) 1st 1997 An Cho-yeong (d. Kim Yeong-sam 1-0)
It seems the earlier tournaments' final was a one-game match.