Originally Posted by
A.Winthrop
.I hope this is correct as yesterday I reused a protruding-
style pin on an excellent condition Shimano UltraGlide chain from the mid-'80s.
As a general rule, any pre-8-speed chain can have pins reused with no problems. I used to do it routinely with Shimano and Sedis 5 and 6-speed era chains.
It is important not to push the pin all the way out of the far side link (as the OP has discovered) since restarting a pin from scratch is very difficult.