Don asked about the tang projecting on left side Simplex dropouts. That's to help facilitate a fast wheel change. It follows the contour of the derailleur hanger's front side. Surely Mssrs. Poulidor and Anquetil were grateful those things were there when their mechanics were all adrenalized and fumbly while replacing rear wheels!
I'm curious - do we know when the left side guide tang appeared and when it disappeared? I want to say it's a late 60s to about 1971 thing, but that's just a very unscientific guess ...
Russ Fitzgerald
Greenwood, SC, USA
http://internaldetours.blogspot.com