I don't recall the model number - it is years old and was bought for a good price used. Basic variac for speed control. You need to manually adjust the speed depending on if you have dumped in too much dry chemistry at once so the stirrier bogs down. Too fast, and it whips air into the solution, which is a nono for developers.
I added a heater salvaged from Bunn commercial coffee warmer to the underside of the stirring platform. It works best to hold temperatures, rather than actually heating the solution in any reasonable rate. Usually I mix in a 3.8L stainless steel beaker, or a 2L pyrex beaker or erlenmeyer flask if the solution needs to stay hot and mix for a long time.