Autocycleplane
Cruisin' on my Bluebird
When did Schwinn start/stop doing this practice?
37-39 for sure. Not too many pop up so tough to say for sure. I'm not even sure every bike got one, or how they were used, etc. They do typically have the bike color on the back of half of it, Jason (Obi) smartly hypothesized it was likely left sticking out of the top of the seat tube when the bike was sprayed. You can see the tan, blue, and black paint on some of the ones above.
One thing I have learned from the build sheets that do exist - the specs in the catalog for the bars, pedals, and seats vs. what is on the build sheets is quite different. A couple of these were pulled from boys bikes but have juvenile/ladies spec bars, and/or pedals. I also love seeing my favorite 30x12 SB bars as original equipment on some bikes, especially when one of them is mine. Also that Gillette Bear tires were a pretty popular tire it seems.