The current version of gnumach advertises itself as 1.2 (version in changelog.Debian.gz: 20020421-1). Except for the announcenment I haven't seen 1.3 anywhere. That's because there exists an small typo in the version string in GNU Mach 1.3.x. If you look at ftp.gnu.org you will see the 1.3 tarball there (and if you look at the version string in that tarball you will notice that it says 1.2.x :).