Well, I’ve never seen one either. I suspect the pulley is probably two pieces which are pressed and glued together in the middle over the central hub and that they’ve separated. At this point, the tension of the belt in the grooves is holding it “together”, but I’ve ordered a new pulley which will arrive tomorrow. Easy enough to swap the new one on.

I’ll post a pic of what is going on with the old pulley once I remove it to give you a visual.