The 115NO60 is a thermal delay switch. From the application of the heater power the bi-metalic strip will heat sufficiently to bend and make contact with the static electrode in 60 seconds. The details of the device are encoded in the Type designation - 115 volt heater, Normally Open contacts and a delay of 60 seconds.
The main application is in providing a delay in the connection of anode volts to mercury vapour rectifiers - thus giving a suitable time for the rectifier to be hot enough to operate.
The heater is broken and the coil of wire is hanging down on the right side of the image. It should be sitting in one of the slots in the ceramic insulator. The timing adjustment during manufacture is by the screw on the fixed contact.
The back of the fixed electrode.
The Type designation is etched into the top of the envelope.
The wide glass tube envelope is 28 mm in diameter, and excluding the IO base pins is 68 mm tall.