The Ths49 is a thermal relay. The contacts on this exhibit are normally open and should close when the heater is activated.
At 6.3 Volts applied to the heater the inverted V glows red hot a small movement of the contacts was observed but they did not close. The current consumption was one Amp. At a current of 1.5 Amps the bulb became very hot. A second application of the current limited power supply caused the filament to shatter.
Since when cold the contacts are open, this relay could be used in series with a power valve to disconnect the HT if the heater supply fails.
The c1 fixed contact is a circular pad attached to the metal frame. The heater connections pass through the insulators seen at the base of the frame.
On the right is the inverted V of the single strand filament.
The filament passes round the glass insulator at the top.
The wide glass tube envelope is 28 mm in diameter, and excluding the IO base pins is 68 mm tall.