Ck,

You are correct, there were no POHs officially until roughly 1976.
Prior to that everything was usually referred to as Owner's Manuals and
the format was not standardized and there were many philosophies as to
what to place in one. A huge number of companies and engineers felt
that Owner's Manuals were to be kept short in the hopes that the owners
would actually read them. Also, some of the numbers for cruise
performance were dreamware - notably Piper and Maule, with cruise
speeds inflated by as much as 20 mph. Cessna had a rep for having
accurate information in Owner's Manuals, Navion put out one of the best
manuals.

Your 150F had an Owner's Manual. It was NOT serialized. It is NOT
required to be in the airplane. It is not part of the equipment.
Prior to POHs the limitations of the airplane were contained in the
weight and balance documents and the placards on the panel and color
coding on the instruments. The good thing is that if you lost the
Owner's Manual, the airplane was still airworthy. The bad thing is
that the Owner's Manuals did not have as much information as the POHs.

Hope that helps,
Rick