The old Plastik Flex Coupling from 1974. It had to be removed to dismount the old stuffingbox and Volvo Blackjack.
BUT!!! It could not be removed. I used a 8" puller, that just bended! So final solution was to cut it off, with the deathwheel (anglegrinder). I used 10 discs to cut it into more pieces. During the whole process, the rubber started melting and smoking - which made the other sailors around me think, that my boat was buring. Furthermore the rubber was spread all over the bilge area, and my hands. Took me forever to get that nasty stuff removed again!