I thought the 117 was the heavier brother of the 217.
The 117 was slightly beefier and as a result its weight went up a touch.
The differences between the 217 and 517 appear minimal, and they both suffer with a tendency to crack at the eyelets. Having said that, I still use a set of 517's as the cracks never got any worse - they look like little fractures, that's all.
The 717 was the last one, and although they appear to have corrected some strength issues with the 517, the only notable difference is the type of ceramic coating used.
1990 Marin Team Titanium, 1991 Marin Team Titanium, 1993 Marin Team Titanium, 1994 Marin Titanium FRS, 1995 Marin Team Titanium, 1995 Marin Eldridge Grade, 1996 Marin Team Titanium, 1998 Marin DH FRS, 1999 Marin Team Titanium, 1999 Marin Mt. Vision Pro, 2000 Marin East Peak, 2002 Marin Mount Vision
1988 Concorde Colombo, 1997 Colnago Master Olympic, 2005 Look KG481-SL, 2009 Look 586
WANTED: Marin Titanium - pre 1990, 1996 FRS, 2007 25th anniversary