GNU CSSC is a workalike for the source code control system SCCS.

SCCS commands implemented this package are: admin, cdc, delta, get,
prs, prt, sccsdiff, rmdel, sact, unget and what. Not all options and
capabilities of the commands have been implemented yet, and the comb and vc
commands are not provided at all.

Unimplemented features include consistency checking (admin -h), ignored
deltas (delta -g), l-files (get -l), and getting a delta by sequence
number (get -a).  Some features like including and excluding
deltas (get -i -x) have been implemented but not extensively tested.