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Our resident Schwinn expert @
Metacortex hath writ that the serials were oft stamped in years ahead so cannot be relied upon to yield actual model years.
The bicycle's stikshift levers began in 1967 so it is unlikely to be earlier.
The reflectors appear aftermarket so it likely predates implementation of CPSC regulations.
Unfortunately, your image is of non-driveside which limits the information it provides to readers.
The backside of the Weinmann model 730 brake calipers may show a date in the form of a clockface device.
Huret began date marking their products in 1978 but cycle clearly earlier so no help there.
You should be able to narrow down date closely by looking at the Schwinn manufacturer catalogues posted here.
Suggest beginning ~1970-72 -
Schwinn catalogs, 1961 - 1970
Schwinn catalogs, 1971 - 1980
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