Is there any indication on the boxes, for which years of M71's they were designed.

The reason I ask, is that the early ones, like my model 71 - 1876 version has a .457" groove to groove measurement with a .437" bore. Yes - .010" deep rifling. The chamber will only accept a .446" bullet, the standard in both paper patched and grooved lubricated bullets. The models of 1884, however, had a .446" groove diameter which shot just fine with the .446" bullets OR the paper patched bullets of pure lead and the same size.
I have read the oversized groove diameters shot OK with paper patched bullets and the 77gr. black powder load due to obturation of the soft bullet. The harder grooved lubricated bullets of later years, however did not shoot well in the deeper grooved earlier rifles.
Yes - the forend had been shortened, probably as it should have been longer, I think and with a metal band/sight at the muzzle end.

As I could not obtain .43 Mauser brass at the time I came across this carbine, I re-chambered it for the .450 Alaskan. I used reasonably equivalent loads in it. Due to the 20" bl. with a 20" twist, it shoots fairly well with all normal bullet weights, including 525gr.FN's. I fired 40 fire lapping loads which enlarged the groove diameter .001" and the bore by the same amount.