Gyroscopic balance? They may have been more in the Chicago area. I believe they were being installed a number of years before I started out. The company I worked for installed many and I serviced them.
For those not familiar they were probably the most advanced furnace made and the engineering is still incredible when I think back on them. They used two stage stats and a resister that would heat and warp a bimetal. This would move a pin if I recall correctly. In doing so the gas would slooowly modulate up to high fire. It was not even 80/20. It modulated. The longer you called for heat the more gas fired.
Even the belt drive motor modulated up to high speed by physically moving the motor increasing tension on the belt. I'll have to dig around and see if I can find a link. You gear heads would have drooled over this thing.