There were some Rocky Mountain bikes that were made with steel lugs and aluminum tubes. They looked pretty nice and I see a few of the about town on a regular basis. The joins were glued (not sure with what though). Not sure the year and model of the bikes either.

The one thing that really catches the attention is the colors of the aluminum tubings next to the lugs. I have personally seen a purple one (a few times), a blue one (regularly) and a black one (once).