Thanks for the info, I've added yours to my list of about 30 so far. It is interesting to note that this is the earliest serial number I've recorded so far, however since Schwinn stamped head tubes with serial numbers before being welded into frames the serial is not a clear indication of the mfg. date.
There were 2 different generations of the 10-speed demonstrators. The 1st gen. A2200 model was introduced for sale in the March 1964 Reporter (dealer newsletter) after having first been seen a month earlier in a sales meeting photo in the Feb. '64 Reporter. A photo in the April 1964 Reporter showed one on the counter at a Schwinn dealer. A redesigned 2nd gen. AB-115 model was introduced in 1967 and had several changes over the production run which finally ended in 1976.
This means yours was most likely built in early '64. Note that it is missing the spoke protector and the hub, freewheel, front and rear derailleurs, chainrings and probably the chain are not original as they are all of much later vintage. The original components were "Sprint" branded.