GTs58
I'm the Wiz, and nobody beats me!
I have 2 Corvette 5 speeds in my Registry that had the Butterfly bars. I haven't come across any literature that states these were a Schwinn factory option, so I'm thinking they were a Schwinn made Dealer accessory that would be purchased and installed at your local dealers. These bars don't show up in the 1962 parts catalog which I find kind of odd.