The spring end-stop that fits inside the restraint tube:
Fitted, with a very sharp piece sticking out of the slot. The restraint can be fitted with this in-situ, withdrawing is another matter:
Not possible to remove (without destroying it) unless you first remove the head-restraint:
Same spring-clip inside the restraint tube, but in this case with the upper edge having a slight downwards angle it was easy to tap it up inside the seat tube with a hammer and wood drift:
