This can confuse even the long timers. Generally, the lower-to-moderate end U.S. made bikes, from forever ago until the mid-'80s, are .833 stem bikes. The top of the line Paramounts and the imported (Japanese and Taiwanese) bikes used the 22.2. It was not until Schwinn moved U.S. production to the Greenville MS plant that they adopted the standard, but I could be wrong on this. It may take a Schwinn maniac, of which I am not one, to detail the specific models and years. When dealing with the '80s-and-earlier bikes it's best to have a caliper on you or be prepared to yank the stem to check the markings.