Happy new year's compadres!
I thought I would dig out an original Winchester 1873 carbine and compare to a Miroku side by side. I recall that the Miroku guns were modelled after the Uberti rifles and carbines. That is a bit odd, but I believe it to be correct, with a few exceptions.
Here are some things that are the same. The Miroku is based on a third model style receiver with integrated rail for the dust cover. The barrel length on both carbines in 20 inches, which was standard. For some reason, the Uberti carbines have a 19 inch barrel. The front sight is on the barrel, which is correct for a Winchester third model carbine. The current Uberti carbines have the front sight on the barrel band which is not correct for a third model style receiver.
Here are some differences. There is a noticeable gap between the barrel and magazine on the Miroku. I believe that is a feature of the Uberti guns as well. I don't understand it. Miroku had a chance to make it right but didn't. Oh, well. The lever and hammer should be case hardened, but are blued on the Miroku. The Miroku has a rebounding firing pin. Probably the lawyers insisted on that. The Miroku has a front sight blade held in by a pin, so it can be replaced. On the original 1873 carbine in my collection, the front sight is integral with the base. Also, the barrel and magazine tube should be even with each other. On the Miroku, the magazine tube is slightly shorter. Finally, the Miroku has a shorter action than the Winchester. I don't understand why they changed the stroke of the action.
Overall, I think the Miroku 1873 carbine is a fine effort. They could have made a few things closer to the original, but I do like it.
Original 1873 carbine on top, Miroku on bottom