This is what I found. Seems to match the sequence you have. Surely the experts will chime in.


Determine the Manufacturing Date


Capacity Added for the Boom Years

Month Code: This one letter code corresponds to the month with A=January, B=Febuary and so on. Because I is not used, September=J and December=M.
Year Code: This two digit code is the last two digits of the year – 86 is 1986.
Sequence Number: This two digit number represents the nth frame and/or fork scheduled during the month. During the peak of the bike boom, Schwinn would add another digit, sometimes producing as many as 500 frames a month.
For example, H7634 is the thirty-fourth frame or fork scheduled during August of 1976.

Edit: http://www.cyclofiend.com/cc/2006/cc...lubin0706.html
I have an '84 Schwinn LeTour Luxe that came win an '85 paint job. Mfg date April, I believe.