Parallax was the same then as now. Due to the low power of the scope it was not as much of a problem, but was present. The shooter could have set his scope to be parallax free at 100, 200 or whatever yardage he preferred, but it was not readily adjustable. As mentioned the problem gets worse as the power goes up, so your Unertl scope has a focusing ring on the front to eliminate parallax at the distance you are shooting.
The Leupold Mark 4 M3 has side focusing for parallax adjustment.