wow! That is a pristine Intermatic 7 day mechanical timer.
The same company made timers for RainSoft, Fleck and others years ago.
Unfortunately chances are good that the only part that is worn out is the index lever.
Manual Regeneration tab with red arrow.
These have not been produced for over a year and are impossible to find.
I have searched and searched.
I hate to say it, but it's time to retire this workhorse and get yourself a new metered softener.
Let me know if I can be of further assistance,
H2OMAN