Sweet's catalogues
Two years ago, about the time I joined aw.org, I went to every library in my area, including the Yale Art and Architecture library, where I spent many a happy afternoon decades ago, going through pages and pages of the current Sweet's catalogues, and discovered that, as you said, nobody seems to keep back issues of them, they're just too big to store. I even called Sweet's corporate offices in NYC and was told to forget it. If you know anyone with a collection that goes back to the late fifties, let me know where they are, I'd love to look at them. My next attempt is going to be to GE's museum of electrical innovation in Schenectady NY. I was told they have archives there. We'll see.