Thanks for posting this.  Like so many threads here, it's an opportunity to increase my knowledge.  

Anthony said
First of all, I want to thank all you gentlemen for not only answering, and stepping up to the plate, so to speak, but the volumes of knowledge that came forward is second to none!
Chuck, TR, Bill, Bob, and Jeremy,
The WACA Forum just keeps on rolling out, information along with it's quality opinions!
Bob,
Thanks for setting me straight on the "+", stamping on the firing pin. My assumption was premature! The slots make sense to me now as a flat bladed "turn screw", would certainly do the trick! I would imagine it's a fine thread and maybe proprietary to Winchester.
Bill, 
With you're pictures and explanations, you certainly spelled out, the difference and similarities of the M-1876, as I wasn't sure.
Chuck, I completely understood you're point, and TR, I am in full agreement with you, as far as being a step that wasn't needed or required as Winchester, previously thought!
Tony
  

Just to be clear Anthony, I did absolutely nothing here!

Chuck, TR, Bill, Bob, and Jeremy,

The WACA Forum just keeps on rolling out, information along with it's quality opinions!

Bob,

Thanks for setting me straight on the "+", stamping on the firing pin. My assumption was premature! The slots make sense to me now as a flat bladed "turn screw", would certainly do the trick! I would imagine it's a fine thread and maybe proprietary to Winchester.

Bill, 

With you're pictures and explanations, you certainly spelled out, the difference and similarities of the M-1876, as I wasn't sure.

Chuck, I completely understood you're point, and TR, I am in full agreement with you, as far as being a step that wasn't needed or required as Winchester, previously thought!

Tony

Bert

Bob

The Bushing on the first models like the top photo of Bill's post you can see a slot on each side of the firing pin. With the pin removed you can put a common screwdriver in it and its threaded in. The bushing has a radius milled on the inside end of it that matches up with the radius of the pin so it had positive stop going forward.  

What I understand is the 123 or CCC were 3  inspections or tests done to the barrel and was not the violent proof. You first had the CCC then for short time they had +++ right about the start of the 2nd model the the 123 showed up along with the VP proof.

I have seen the + on firing pins but not all and I have seen it on first model pins and on later ones. I never did a in depth look at it taking firing pins out to see if its a serial range thing but I would doubt its a replacement indication. My guess it was a inspection mark. 

Bob 

How about you?   Do you have any rifles or shotguns that were featured in the book?  A previous owner's collection still counts.

Anthony said
In regards to these two models, and especially the early model 1873, as I'm not sure about reason that the "Bushing", was used on the bolt, face where the firing pin extrudes, or strikes the cartridge, in the closed breach. These are evident naturally when the breach is opened, revealing the bolt face. I am aware that Winchester did modify the design on the later model 1873's, and eliminated the bushing.
Not sure if the early M-1876 had this or not? Bill Hockett, please feel free to add you're comments on this! 
So my question is for Bob, (1873 man), TR, and others to comment here, why was it used or what was the purpose in these early designs?
Was the bushing a hardened material, (steel), for wear purposes, that Winchester decided possibly wasn't needed?
Tony
  

Tony, apparently the Model 1876 followed this design change like the Model 1873.  Madis backs this up on page 233 of my 1 of 1000 edition of "The Winchester Book."

See photos below.  SN 9911 is a second model and has the bushing.  SN 33812 is an early third model and has the solid face breechbolt.

Henry Mero said
Yeah Mark ,You're about 7 hours from Seaforth/Egmondville, down on the other end of Lake Huron. I am also planning on attending the Ohio show, if Donald will let Me in to the country.
  

I don’t know Harry.  You are a  very suspicious looking character. 

You'll enjoy it! The OGCA/WACA Show is a nice get together.

Tony