Those are the same rockers that I had so much trouble with in the early 90's. The roller tip pin is held in place by pressing a tool in the end of the roller pin causing it to expand and stay in place.
Over time they loosten up and, if not caught and changed, they break!
If you are going to use them make sure you take a close look at the clearance around the spring reatainers and pushrod cup during the full sweep. Those rockers are real tight on clearance and the pushrods (Crane??) have a fairly wide top edge to them. The spring retainers and Crane pushrods have no clearance issues with the Crane Gold Race Rockers. I know, that's what I changed to!
P.S. You should probably have 2.5 threads showing, if you can't, the pushrods are too long. Shim the shafts up for the correct geometry and then check for the required pushrod length.