My second set of 24212 SL from Glenn.
I think the SL (super lux?) means it has an anti tamper rotating sleeve on. I ordered from .org on-line shop just before Dave, so we'll see what turns up. I've measured my 24212SL, and it seems to have 4.4mm clearance, so perhaps the end popped off because the thread was well lubricated and the thread is a more precise fit and hydraulic action popped the end off?