As mentioned by Jen, each aircraft produced after 1977, when the aircraft manufacturers went to the GAMA format manuals, must have a Pilots Operating Handbook (POH) specific to their airplane in the airplane to be airworthy.
With the adaptation of the GAMA format the manufacturers, recognizing that sending each student pilot home with the serial number specific POH would soon cause damage to it, started publishing Information Manuals.
The information manuals had all the same information as the POH, but was not usable as a POH.
Earlier pre-1977 airplanes did not have this requirement for airworthiness.
