In the 50s, 60s and 70s, Waring sold lots of blendors with fixed blades in department and other stores, not just as bar blenders. Higher end models began to feature snap out blades in the 70s then the line began to go over to screw off blade assemblies in the later 70s. Cleaning the thick stuff like peanut butter was possible from fixed blade jars, but scooping out stuff stuck in the region of the blades was time cousuming, ate up rubber spatulas and left far higher amounts of wasted product stuck in the jar.