12 Day Skipper Wheel Used on the Fleck 5600 Valve ( 12 day version, not Econominder version ).
And also the Fleck 3200 Timer Assembly ( used on many different Fleck Models ).

How to Set
The 12 numbers are only reference points. The wheel moves one position each night at 2 a.m.
And IF the PIN is slid OUTWARD, the Timer will start a Regeneration cycle. If the pin is not out, nothing happens, except the number advances ( counter clockwise ) one position.
The Red Arrow is pointing to the PIN that will either Start Regen ( if OUT ) or do nothing ( if slid IN ) that night.
Common sequence to set would be every 3rd or 4th pin out ( resulting in regeneration every 3rd or 4th day ).
The “Proper” frequency of regeneration is based on the water quality being treated, the size of the Tank, and the Amount of water being used each day.