Re: SCCS hits you
Tag expansion also happens in RCS, CVS and Subversion (in the latter it has to be enabled in the properties of the file). The difference is that the tag trigger notation in these ($id: ,,,,$ and some others) stays in the file, in SCCS the magic strings expand to version numbers without the triggering character sequence.
Git lost this feature, because it is seriously contrary to its idea of identifying versions with a hash of the file contents. Expanding a version tag would make the file be of a different version in the eyes of Git. A loss, because the embedded file version numbers have often saved my sanity by allowing a compiled program identify what file versions it has been put together from.