SGL stands for Samual G Lenhart. He and his son were heavily involved in the production of the 2 G3s and the two 5car trains. For whatever the reason, Sam was anti-flywheel. Maybe b/c he was really old school? I don't know. I'm still trying to run the story down on these 2 sets. They ARE drop dead gorgeous, and must haves, especially if you are a Reading steam fan!
Chris
LVHR