I was busy with a pipe that I was going to fit an endcap to, this afternoon, when this happened...
Normally I turn a little tenon on the shank when I'm planning on using an endcap, then fit a scrap piece of briar over with a spot of CA glue to keep it in place while sanding. This is done so that I end up with smooth lines towards the end of the shank, instead of rounding it over, which is bound to happen when doing it without.Under normal circumstances (today I use the term lightly), I put the scrap end into a vice and with a gentle but firm twist, break the unwanted piece off. If you look closely, you'll see part of the briar tenon on the left in the scrap piece and the broken bit on the shank end of the stummel. A bit of the CA glue must have gotten where it was not supposed to go, onto the tenon and not just the face.