To retrieve a writable copy of an earlier version, use get -k. This can be useful when you need to back track past several deltas.
To use an earlier delta as the basis for creating a new one:
Check out the file as you normally would (using sccs edit).
Retrieve a writable copy of an earlier "good" version (giving it a different file name) using get -k:
sccs get -k -r sid -Goldname filename
The -Goldname filename option specifies the name of the newly retrieved version.
Replace the current version with the older "good" version:
mv oldname filename
Check the file back in.
In some cases, it may be simpler just to exclude certain deltas. Or refer to "Branches " for information on how to use SCCS to manage divergent sets of updates to a file.