I agree, it is an 1873 and it is a replica. (However, the originals were not chambered in .45 Colt. This is a chambering that replicas introduced.)
Proof in the pudding is had by closely examining the receiver: If you note this original receiver:
http://upload.wikimedia.org/wikipedia/c ... 3_open.JPG
(I'm not posting it because it will loose too much size), not where the screws for the trigger and hammer pivots are. Then compare this with a modern Uberti replica:
http://www.uberti.com/firearms/images/1 ... fle_lg.jpg
and you see that there is a single large screw head above and behind the trigger, just like the one the girl is holding. This may not be so evident in the attached picture, but looking at the original here:
http://olegvolk.net/gallery/d/33899-1/d ... 2_5552.jpg
this is much more obvious.
The toggle link action was weak and its geometry limited the length of cartridge that could be used. It was already pretty old by 1873 (
http://en.wikipedia.org/wiki/Volcanic_rifle) and it was quite weak, compared to the later designs of John M Browning with the M1892, chambered for the same class of cartridges as the 1873 and much smaller.
In order to take larger cartridges, Winchester came out with the 1876 "Centennial" model (the USA was 100 years old that year), but even enlarging the action still didn't permit this rifle to use the .45-70 round, which was too long. Instead, Winchester came out with proprietary cartridges that were less than 2 1/4" long and those who wanted a .45-70 lever action had to wait for the Marlin 1881.