The trouble is, weller changed the wiring of the iron cable, and effectively put the sensor over where the element was, so if you plug an old iron into a new station or vice versa you blow the temp sensor, which is expensive
A resistance check is not a lot of use 'cause they measure around the same. However on the cable the sensor pins are gold in colour and match up with the gold coloured sockets on the stand socket.
An advantage about the older irons is there is a lot more tip metal in contact with the heating element so better heating. The new irons just have the small tip base, a circle around 6mm, to transfer the heat.
Ken