I don't know when it changed. I understand the post-64s were two piece, as well as ther 1992 classics. It went back to a one piece sometime when the traditional M70s were made, either in SC or Portugal.

Here's photos of some of the boltsa from my other Portuguese M70s.

[Linked Image from i.imgur.com]

[Linked Image from i.imgur.com]

[Linked Image from i.imgur.com]

Clearly, the handles and bolt bodies are one piece.