cjpacitto,
Excellent closeup pictures and lighting.
I like the division of groups.
Group 1 would be the "normal" feel for the used lifter that is not left "pumped up" by the engine. Your explanation is similiar to Bennington Motorsports--
Bennington Motorsports
Group 2 is what I have always wondered about.
They are fine, reuseable. The lifters are in a "pumped up" stage. The piston rebounds after being pressed by the vice.
Group three is not useable because the piston cannot rebound and the cause is uncertain.
Excellent work on cutting them apart.
John