Anybody ever work on the reach-in wall freezers at McDonald's? To my understanding they are quite old (over 20 years) and not many of them are around. I have no idea who manufactures these things and I would like to get some info on them such as possible model numbers and how much gas do these things hold. We use Hot Shot as an R-12 replacement gas and I would like to know how much gas these things originally hold. Sure they are TXV/Receiver systems, but I want to know what the original charge is supposed to be.