Hi Dan,
Welcome to the forum. I got my first GBD, (a second, actually--City de Luxe,) in 1961. It cost $10, and was a birthday gift from a girlfriend, and was a real budget stretcher for an undergrad. Since then, I've picked up about a dozen, most made in the 60s and early 70s. The Collector series was one of their better lines, but there is such a variety and assortment of GBD pipes that it's often difficult to tell where and when a pipe was made. One clue: if it has a solid brass or silver GBD rondelle set into the stem, it's one of the earlier (and better, IMHO,) models made prior to the merger with Comoy. If the rondelle is painted or stamped, it's a later model, and probably not of the same quality. And by quality, I mean a pipe that served as a gold standard during its heyday, rivaling Dunhill and Charatan at their best. You can find a lot of useful info at pipedia.org.
My guess: you've got a great pipe, one of GBD's better ones.