DRF aka Thrifty Bill
Join Date: Jan 2008
Location: The NC Mountains
Bikes: 86 Katakura Silk, 87 Prologue, 87 Cimarron, 14 frame school custom, 73 Paramount
There will be four numbers on that head badge, first three are the day of the year, last one is the year. So 0907 would be the 90th day of 67, 77, or 87. Knowing the right decade comes from knowing the era of the bike.
Now I do not know how far that date coding process was used at Schwinn. I typically have bikes from the 1970s and 1980s, they all had them.