I have not tested this unit. This Vintage GE Oven Temperature Tester is from the Olmstead County Maintenance Department. They have adopted the Lean Principle and discarded surplus, unused equipment. Overall, you can see it is great shape, both inside and out. The probe shows signs of it's age but the case is in very good condition. The clip is not connected and i am not sure if it supposed to be. Please see pictures for they are an integral part of the description.