What is this piece?

[BLU]

I've been doing a complete take-down/cleaning of my S&W revolvers. My 629-4 3" has never been disassembled, (it's a PC piece so I didn't mess with it until now). After removing the trigger, I saw a piece I was unfamiliar with. Hmmm... I checked my Kuhnhausen manual and didn't see it listed. Best I can figure is it rides under the trigger and moves upward and under the Cylinder bolt/hammer block when the trigger is pulled. It looks to be a redundant block when the cylinder is open. None of my other N frames have this.

Picture #1. The piece in question.
Picture #2. The piece in position.
Picture #3. The trigger in place, (which has a pin on the underside that fits in a slot on the piece).

What is this piece and what is it's designed function?

 

[BLU]

Pic.

 

[BLU]

Pic 3

 

[sgt127]

Going on memory here. It's part of the enhanced durability package. It keeps the cylinder latched shut under hard recoil by keeping the cylinder release from bouncing backwards. It's engaged at full cock, or, full rearward trigger pull.

 

[rcmodel]

Yep, that's what it is all right.

I'm not sure what they call it either.

Rc

 

[BLU]

Enhanced durability. Okay, yeah.... I'll run with that. Compared to my 329PD that's only a few ounces heavier than my Chief's Special, this 629 weighs so much more with it's un-fluted cylinder. It never occurred to me that S&W would do that, but, it makes sense. Still, I wonder why it's not a labeled part on any of my diagrams. Thank you for your input!