It is a brass doorstop: Basically a 1 inch brass rod with a M6 threaded hole down the centre. It's just about the right size to make a heater block! And, it's reduced to £3!
I picked one up to play with.
Closer inspection revealed that the central threaded hole projects all the way through the block, stopping at the small indent for the O-ring.
I hacksawed through at the indent, cutting off a 20mm chunk - the m6 thread goes right through.
I drilled a couple of 6.5mm holes through for my resistors - and widened them a little, as my resistors are not straight, and added a small hole for a themistor.
Widening half the m6 thread to m8 allows me to screw in a Peek insulator.
Here's a pic of the components:
Firing it up, I found that it reaches 220C in about 7 minutes, with no insulation. The heater seems pretty sturdy and well-attached. Starting up my (fixed) BfB extruder drive, I waited expectantly....
Hurrah! It extruded several cm of filament - reasonably quick too!
If it starts up again later, then I might be able to build something soon!
Extrusion: 220C at motor speed of 120/255. Nozzle 0.8mm welding tip, 1.01mm filament