Here is my 1984 Toro model 20672 21" rear bagger 3-speed Deluxe Pow-R-Drive (rear drive) self-propelled walk-behind mower with BBC (blade brake clutch).
I had such fond memories not only of this but also my Dad's 1973 Sears Craftsman Eager-1 9026 walk-behind, as well as my next-door neighbor's 1962 Toro Whirlwind Pow-R-Drive 20122 mower (which he had until 1988; the side bag I saw on it was a mid 1970s replacement) and circa 1964 Sunbeam RE-18S electric twin blade mower, and my other neighbor's circa 1972 Snapper V210 and circa 1975 Jacobsen Turbo-Vent mowers.
However, regarding rear baggers like mine, this one uses the Toro TNT100 (by Tecumseh) 4-cycle engine, whereas the Suzuki-built GTS120 2-cycle engine had an edge over the TNT100 in reliability as well as having a unique sound.
~Ben