For libc5, run "man libc" and look under the heading "Linux libc".

The latest libc5 package is from 2003 in debian-archive, from what I
can see:
debian-archive/debian/pool/main/libc/libc/libc5_5.4.46-15_i386.deb
That is within Debian 3.0, Woody, timeline.

Regards,
/Karl Hammar