This North Central Airlines artifact is indeed rare. Described as a pinback, this Herman I would really describe as a brooch. It was worn by North Central flight attendants as part of their uniform. How far back it goes, I am not sure, but here is an image of mine from a Northliner, in-flight magazine. You can clearly see the brooch. It sold, not surprisingly, for $120.00 on eBay from a seller in an old North Central town, Brainerd, Minnesota.
This artifact found on eBay is described well by its seller:
North Central Airlines Original Douglas DC-3 Flight Manual was first issued in 1957 and revised July 1, 1961. is tabbed into Chapters divided into Sections. Chapter 1 covers Aircraft, Engines, Carburetors, & Propeller. II has Instruments, Fuel System & Hydraulic System. Chapter III covers Heating and Ventilating System, Electrical System, Radio, & Auxiliary Systems, Chapter IV has Operating Procedures, Approach and Landing , Landing Roll -Icing, Thunderstorms & Turbulence and Weight & Balance. Chapter V covers Emergency. Procedures. It is still in an old 3 ring notebook but the cover spine has been taped. Otherwise, it is in excellent condition.