It's a custom cue & I believe it was added later. I did also post in cuemaker forum.Brand of cue? Ask in the Cuemaker section too. Based on those pics i don't see any threads in there that would give a clue to an ext.
I can't budge it by hand. Is there allen that fits it?If it is just unfocused and there really are threads in there, you may be able to unscrew the bumper by hand.
It looks like this bumper which has 3/4-10 threads.
View attachment 743450
I can't budge it by hand. Is there allen that fits it?