A friend brought a 21st century sealing iron over to the house for me to show him how to shrink plastic covering on a arf. I have used a Top Flight iron for more then 30 years. Using a Coverite pocket thermometer to mark the temperatures on the Top Flight  iron. I know there  is a 30 to 40 degree difference in the thermostat when it reaches temperature and recycles. The 21st century iron has a thermostat that is marked in degrees and matches exactly with the pocket thermometer but the main thing is it holds the heat with in 5 degrees of what you set it at. With the Top flight iron you would be ironing monokoe and it would be sticking good then all of a sudan it would stop sticking I would have to wait a few minuets for the iron to reheat or boost the temperature up , with the 21st Century iron this is a thing of the past. I highly recommend it
Willis