[Mike of the Mountain]

Originally Posted by Brian Dudley

Odd... as I recall, nearly every parker I have had re-cased has had it.

Yes, it is dependent on the case hardening process. But more a function of how the trigger plate is machined. The channel in the plate for the unhooking slide results in a dramatically different thickenss of material up the middle of the plate. This is really the main reason for a difference in the appearance and patterning of the colors in that area.

And I will add that not all original examples are that pronounced. Every gun is different.

Good call Brian. Makes sense that any difference in metal thickness would cause temperature fluctuations.