El Paso K-series Weavers vary considerably in construction, the reason many hunters have had mixed results with them. The older models didn't have ANY coating on the lenses, weren't sealed against moisture, and sometimes had iffy adjustments due to weak erector springs. They still sold well because there basically wasn't much competition at their price-point for a long time--in fact Weavers pretty much dominated the scope market for the "average guy," because they were so affordable. But they're also one of the reasons so many hunters experienced "fogged" scopes and adjustments that weren't exactly consistent--and so many believed you had to beat on adjustment turrets after you turned them.
The later models were sealed, had coated lenses and much better adjustments. I have several, partly because they're an even better deal than they were back then, and use them on my more traditional hunting rifles. The K4 on my pre-'64 Winchester Model 70 Featherweight .308, for instance, has very consistent adjustments--though they're 1/2" instead of today's common 1/4" or 1/4MOA. It has coated lenses, though probably only single-coated, and is sealed against moisture. It also has a plex-type reticle, one of the most reliable indications of a later-model K-series scope.
