Joined: Oct 2008
Posts: 659
Likes: 232
From: Tidewater VA
Bikes: 1975 Raleigh Gran Sport, 1978 Bertin C35, 1982 Trek 614, 1983 Trek 620, 1984 Nishiki Seral, 1995 Mercian Ko’M, 1998 Fisher HKEK, 2000 Rivendell RS, 2001 Heron Touring, 2016 Nobilette Custom
Simplex derailleurs from this era came in three cage lengths:
CP - short, T - medium, and GT - long.
The /P or /SP designated whether the derailleur came with a mounting plate or not. So for instance, a GT/SP derailleur was a long cage derailleur without a mounting plate.