Just got an old Jadeite Sheaffer Flat Top and noticed something odd about it when cleaning the pen.



Notice anything funny? Go on, I'll wait.

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There is no serial number. As opposed to other flattop seen here:



What?! anyone have information on this? The one without the stamping also appears to be an oversized model and is a bit girthier. The no-serial-pen seen above the serial-pen here:



Any thoughts?