The letter prefix on the model number would help determine the age. As I recall, the Whirlpool dealer for whom I worked had a dryer like this at his house in town next door to the shop. Something must have been wonky with the pushbutton temp selector, or maybe with one or more of the four bi-metal thermostats that would have been involved for the four temps. His wife always had it set on the lowest temp button. Maybe the thermostat for that circuit had been replaced with a regular-temp thermostat.