1860/62 design question

[condorsp]

At a gunshow last weekend I got a Pietta 1862 Sheriff 44. While looking it over I noticed a few features I had never seen before. So, I looked over all the 1860's and 62's on GB and found that some of the repros have these and some not. All the Colts have them.
I'm wondering what the purpose of these are. The recoil shield (I think that's what it's called) on both sides is cut at the bottom. Was there a reason for this?
I've had a few of these type revolvers over the years but never noticed this...

Condor Jonn

 

[Norinco]

The recoil shield cuts are for the shoulder stock.

 

[condorsp]

Thanks NORINCO. Clears that up for me...

 

[Norinco]

Make sure they have the lug screws on the frame as well. Otherwise the stock won't attach.