No question it's part of the first/original factory stamping and not some sort of dealer inventory mark added later. Also, the shape 59 was, and still is, a standard. What's your best guess about the "/1-37" following the shape number? (Everything about the pipe is normal, btw. No unusual stem shape, connector, filter, or the like.)
Muchacho gracioso. ::
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Muchacho gracioso. ::
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