Sorry I'm late to the party, but I always invite myself when Model 1's are involved.
As others have said, this is a remarkably well preserved Model 1, 2nd Issue. Based on my database, serial number 84xxx would have shipped somewhere in the vicinity of January or February 1866. This is almost irrefutably the original finish; sterling silver plating on the brass frame, and a bright blue finish on the cylinder and barrel. Other than a light oiling or working with Renwax, please don't do anything else to the gun. It's perfect.
The case is rough, but even in this condition It'd fetch at least $500 in its present condition (and by that, I mean that I'd stroke a check right now for $500 for it). The broken and missing pieces are problematic, but I'd want to hold it in my hands to decide whether or not it's a candidate for restoration. If not, I'd give it a very gentle cleaning and display it as is. The green velvet appears to be all (mostly?) there.
It is worth noting that this is probably not the original gun that came in this box; the gun is about 5 years too late for the box. But, it looks great in there, so I'd just leave it and enjoy it.
As for restored versus original: I'd approach this box with the mindset of wanting to curate it for future generations to enjoy. If at all possible I'd leave it as is, since it will only ever be "original" once and once that's gone, it's gone forever. But if there's enough cracking that the structural integrity appears to be seriously compromised, then I'd consider having it restored, or at least repaired enough to stabilize it.
Mike