>
> > 2005-04-14  YAMAMOTO Mitsuharu  <mituharu@math.s.chiba-u.ac.jp>
> >
> >       * international/mule-cmds.el (set-locale-environment): On Mac OS,
> >       use preferences AppleLocale and AppleLanguages, and variable
> >       mac-system-locale for default locale.  On Mac OS Classic, use
> >       mac-system-coding-system for default coding systems.
>
> But there is no further references to mac-system-locale in the other
> changelogs and it looks like mule-cmds.el does not define it and there does
> not seem to be any place in the Emacs code that refers to AppleLocale or
> AppleLanguages anymore.
>
> So, is that something that's been removed?
>

There are two complete implementations of Emacs on macOS. One originate
from the NextSTEP world and is called the "NS" port, this is the official
version today. The second originate from Mac OS classic and use the prefix
"mac-". Up to Emacs 22, this was the official version of Emacs, but was
removed in 2008. It is still being maintained by Yamamoto Mitsuharu san.

Apparently, the "mac" port supports AppleLocale and AppleLanguage whereas
the "NS" port doesn't. However, contributions are welcome!

    -- Anders