The oldest Armin commit that I found in CPython is:

commit 1b3c04b510c875fd3e31d13b73e76d3702bf99a0
Author: Armin Rigo <arigo@tunes.org>
Date:   Fri Oct 24 17:15:29 2003 +0000
    
    Fixed bug introduced in revision 1.27

@gvanrossum @brettcannon: Guido, Brett: do you recall exactly when Armin Rigo got his commit bit? I failed to find a "promotion" email in the archives of python-dev, October 2003.

cc @arigo

I discussed with Armin. He don't recall when he got his commit bit, nor when he asked to drop his commit bit :-) So I just used the year of his first and last commit as core dev. Hopefully, @arigo still contributes to CPython, now using regular PR ;-)