This is a very early type of power steering gear, with the separate power cylinder and axial spool valve; I believe this is still common on very large trucks today, but in 1959 the Saginaw integral rotary-valve gear was introduced and basically became an industry standard for domestic (and some import) cars up into the 90s, and continued for light trucks after that to this day with some small variations. The accompanying integral-reservoir pump (also known as the "ham can") has also remained nearly the same over that timeframe.