Trapdoor Carbine

Ok, been trying to teach myself something about these, with the hopes of acquiring one. I am having second thoughts, as I see a lot of guns that are just plain wrong, not carbines but rather cut down rifles? Also see quite a few things that do not add up with my limited knowledge of these. A few things confuse me:
1- Is it correct all carbines made after some time in 1886 should be stamped as Model 1884? Is it possible that Model 1873 carbines were made late into the 1880s and early 1890s? I see a few 1873 marked receivers with high serial numbers?
2 - I see listings for model 1879 carbines? My understanding (limited) is that there is no such thing? There are only 1873 and 1884?
3- I see quite a few rifles with serial numbers that would indicate (according to Poyer) a certain year of manufacture, but a cartouche on the stock that is a completely different year. Leads me to think, these are possibly like M1 Carbines, and at times were rebuilt at Springfield or somewhere in the military and parts got all mixed up? Or is that not likely?

Your general comment is correct - carbines have always been scarcer as fewer were made, hence they have been faked. Some cut-downs were simply done for convenience for use in hunting, etc., but others were done with larceny in mind - many crudely, but some with great care. The latter is what you need to look out for. There are certain serial number ranges where no carbines were made, and genuine carbines have certain features which need to be learned. There is not space to list them here, nor do I wish to enable the fakers to clean-up their act. I will vet, to the best of my ability, any carbine offered for sale, for any writer to this forum. All you need to do is ask. Do not hesitate to refer me to a sale listing, as my collection (PictureTrail - Gallery) is complete and I am no longer buying guns, or at least not standard carbines. Now to your specific points:

(1) No receivers were ever dated - you are speaking of the breechblock. The only thing that is different on an 1884 carbine is the Buffington sight. There was a huge supply of perfectly good late (wide) blocks on hand, dated 1873, which were used to exhaustion in 1886/1887. When they finally ran out, it was felt that it would be appropriate to change the date on new production. All later blocks were dated 1884, even when used on the so-called M1888 rod-bayonet rifle, the final version produced. Occurance of an 1873 block past 1887 would be unusual and probably wrong. The only exception would be a few rod-bayonet rifles which were rebuilt at SA using older part. It should be stressed that any receiver or block made after the width change at 96300 would have been considered "acceptable" for use. They (SA) were frugal and concerned with turning out a product, not keeping things tidy for the collectors of today. Context is important - some "mismatches" are totally OK, but others are not.

(2) SA officially recognized three carbine models: 1873, 1877, and 1884. 1879 is a term of collector convenience, and generally refers to those arms having the "Buckhorn" rear sight, which came in a large number of tiny variations. The 1877 is the scarce one and is little understood. It has a special rear sight, similar to the 1873, but with a smooth sloping base, and still has no provision for windage, a feature of the 1879 sight. The beginning of the M1877 is clear, fat short wrist and trap in butt - at about 75000, but the end is nebulous, since it morphs at the sight change at (1).

(3) So long as the stock date is later than the receiver number by no more than one year, the assembly is generally considered as potentially OK. A stock cartouche earlier than the receiver number would be a no-no. Wide variations in dates would most likely be the result of activity outside of the military. While there are certainly still plenty of virgins around, a huge number of trapdoors have been though the mill as it were, over the last nearly 150 years, yielding some strange combinations. I repeat my offer to vet guns offered for sale.

Hope that helps.