Has 20+ years of SLR/camera experience.
1:2 max magnification, M/A switch, build
not super sharp, colors a bit flat
From the specs alone you might think this lens could be a direct ancestor of the excellent SP Adaptall-2 35-80 f/2.8-3.5, but in reality its design and performance are quite different: this one is a 1-touch zoom with a separate macro switch and only mediocre optical quality.
Probably in its day this Adaptall lens was a fairly ambitious design, combining relatively wide aperture with a maximum magnification of 1:2 (even better than the subsequent SP Adaptall-2 version). There is a separate and large switch to alternate between manual stop down and automatic exposure, which facilitates depth of field preview on camera bodies without their own DOF preview button. Build is good, movements are tight and smooth, the aperture ring is fairly wide and easily controlled without having to take your eye off the viewfinder.
Unfortunately, optically this lens is relatively underwhelming. Sharpness drops off noticeably away from the center, while colors are slightly flat and tend to have a greenish hue. This lens would be a good choice if you specifically want to reproduce the look of 60s or 70s color prints, but for almost any other purposes the SP Adaptall-2 will serve much better. Other drawbacks are that the macro range needs to be accessed via a locking button, and at maximum magnification you are left with only 2 inches working distance.