I may have been the last owner of an Ideal Standard "Elan" Balanced Flue Central Heating boiler!
If there are others still squeezing the life out of one, This is my Spare Thermocouple which was squirrelled away inside the controls compartment.
I had two fail in quick succession, so thought it wise to have a spare handy!
Sod's law says if you have a spare, you'll never need it!
I'm sure it will fit several other boilers of similar vintage.
Priceless now, as they're rare as hens teeth.
No guarantees that it'll work, but it most probably will!