TexasCHLforum.com

Finally found an explanation for that 1/4 cock position, which is not a cock position at all.

from Springfield Armory

The Safety Stop is a flat, shelf-like surface on the
hammer which functions automatically. It will engage the
sear in the unlikely event of primary sear notch failure.
This will prevent the hammer from falling fully forward
unintentionally and will insure against uncontrolled
automatic fire. It also prevents the hammer from striking the
firing pin should your hand slip from the slide or hammer
while cocking the pistol, provided the hammer is rotated
past the Safety Stop. It is located such that when the sear
engages the Safety Stop, the sear can be disengaged by
squeezing the trigger. It falls because the sear slides over
the flat part of the safety stop to release the hammer. This
is intentional but will not allow the pistol to fire. It will not
fire because the hammer is almost fully forward when it is
released from the sear. The Safety Stop is not a manual safety
and should not be engaged by hand. Do not carry
the firearm while Safety Stop is engaged.

3 Shelves/notches vs 2

Can't explain the purpose and function of that 3rd notch on some hammers.

Springfields have a quarter cock, 3 shelves/notches on the hammer. No mention of it in the manuals.

Did ya'll settle on the purpose of the quarter cock? I've heard is used for de-cocking and heard its backup catch for sear failure.