Some ...

For a Schwinn published bulletin, this has a few errors:

I. Serial number location:
C. 1952 - 1971 numbers were stamped on the left fork end.

This was moved in April of 1970.

III. Frame design:
C. Flash welding (butt welds on head and hanger projections) since 1958.

I think this has been around since 1949 (at least -- maybe I'm interpreting this wrong?).
http://www.trfindley.com/flschwinn_1...0/1949_19.html

IV. Parts innovation:
F. Middleweights introduced in 1956.

The Corvette was introduced in 1954 (for the '55 model year). Scooper's Dad is on the far left!
http://www.schwinnbike.com/heritage/...chmentid=35602

There is also the anomoly with Bridgestone using place holders for months prior to the model year (for example, November and December of 1982 for the '83 model year would be X3 and Y3, then January would be A3), but this probably started after this Bulletin was published (don't hold me to those years). I think some Panasonic (Japan) built Schwinns also had serials on the headtube (Voyageurs), but that probably came later as well. The '80s dating was crazy! We can't even get a straight answer out of Richard Schwinn.

Bob