NORGE WASHERS & DRYRES
The gas burner had a extra solenoid on it to allow two different BTU out puts. WP did this on thier two speed gas dryers, Wards & norge used a two level valve on thier high end dryers so the heat could tapper down as the clothes dried. This was thier version of KMs soft heat. The 1960s KM soft heat gas dryers had a true modulating burner that tapered the BTU output down as the clothes dried from 37,000 to less than 5,000 BTUs the burner did not cut off completely until the dryer went into cool down. Most gas ovens had a modulating thermostats until about 1960 where the flame didn't go off and on to maintain temperature, it just tapered up & down and most people who are into older gas stoves will tell you how well they bake this is why.