The use of source control management tools is nowadays a standard
practice in the software industry. Furthermore, it seems that there
is quite a strong consensus (for deliverables) to have an instable
branch where new features arrive and one or several stable branches
where only bugfixes are added. I am interested into the history of
the emergence and consolidation of these practices. Can anybody
provide information about the following milestones?

• When SCM was used for the first time in an organisation developing software?
• When was released the first free-software SCM?
• When was released the first SCM shipped by a software company?
• When was given the first talk about SCM in a developer’s meeting
  of international importance?
• Which alternative schemes to the one unstable and one or more
  stable branches scheme are used today, by a significantly large
  community (e.g. a large company).

(Note that if a project uses topic branches, development happens in
numerous branches, but none of them correspond to deliverables.)