Over the years we have used two different versions of thermocouple connectors to connect the thermocouple to the gas valves. The screw fit which requires an 8 mm A/F spanner to remove and the coaxial push fit (looks like an aerial cable connector). Some thermocouple may be a single copper tube style whilst others are a twin wire version.
The critical details are the two end connections.
Screw fit thermocouples were used until about 2008.
Since 2008 all valves have used a coaxial push fit thermocouple.