It is indeed from the latter half of the 1970s.
That is the model SP854A, which was tested by Consumer Reports in 1976. This model, and the Wards UHO 870 (the Wards twin of the Hoover Power Drive Dial-A-Matic) were both recommended in view of their good performance. The SP870A was further praised for its low price, and the UHO870 for its self-propulsion (which was found to be particularly helpful for large, heavily carpeted homes), its convenient automatic pile adjustment, and for being relatively quiet for an upright.