Carbine questions

I am looking at a carbine with serial number 173487 or maybe last digit is 1 ??. It has an early true carbine stock without tool compartment. Rest of gun looks later. No serations on rear sight edges. Low arch block. What else do I need to look at to determine what may be non original parts. Does have 3 notch tumbler. Any way to determine if barrel is correct to action? I am new but would like a carbine with original parts but understand this is very difficult to find. What is depth of rifiling on a very good barrel? Wore out barrel?
thanks in advance!!

Well, for openers, that is nowhere near any other carbine numbers - also what you have described is a very odd combination, and not something that SA would have done.

What makes you sure that it is a carbine stock - need to look beyond the fact that a sling ring bar is installed. Anything filled at the front? Is there a hole in the stock immediately behind the front triggerguard screw (requires guard to be removed)?

The receiver width changed between 96271 and 96309. The wrist, comb, and trap changed about 20,000 before that. How long is the comb, 9.5" or 10.25"? If the rear sight lacks serrations, but looks like the 1879, it is the 1877 and should be graduated to to 600 yds.

Nominally, the bore is supposed to be .450" with grooves around .458", but they do tend to run larger, especially in the grooves. AFAIK, there are no categorized muzzle wear levels. For accurate shooting it's pretty much (1) look for a nice smooth bore with strong rifling (2) slug it, and cast soft bullets accordingly.

Sorry, but you are looking at a mess of parts which are totally unrelated, though it is just possible that someone may have butchered a very valuble piece of wood.