"N.I.B. unfired" and Never fired after leaving the factory, mean pretty much the same thing As jrmiddleton425 has stated, if it has proof marks, it has been fired. But N.I.B., unfired means a whole lot more with a Colt Python, or a T-series Hi-power or a C-96 Mauser... than it does for a common .22 pistol or rifle that was made in the millions and is still in production. "Unfired" examples of the latter two reside in my collection. The Hi-power would be worth more than it is if I had the original bill of sale and the original box. (Actually, I'm told it came in a pouch.") The Mauser has a matching stock, but a missing lanyard loop. That distracts a bit from its value.
Collectors are rather odd ducks. We lust after guns that are both original and high conditioned. By "conditioned" I mean percentage of original finish remaining. The other determining factor is originality. Does it have 100% of the parts it left the factory with? Rareness is not necessarily a factor in desirability. M-1 carbines are not rare. They made over six million of them. But to find one that is both all original and high conditioned is a near impossibility. Same with M-1 rifles. And then there is the "condition" thing. On some high end collectables, say Lugers or Colt model SAAs each percentage point over 97% can dramatically increase the value of the gun. Another significant factor with SAAs is the drag line on the cylinder. A high conditioned piece with no drag lines on the cylinder will bring a fat premium over the same gun that has had the hammer cocked, even once. This is more true for the first and second generation guns than it is for the newer ones.
I have been criticized many times because I refuse to shoot either one of my "unfired" guns. "If I had it I'd shoot the snot out of it." Heard that many times. Well, that's fine with me, except you don't have it and I do. I get just as much enjoyment out of admiring a pristine, brand new example of a classic gun, as I do in firing it. Besides , I've fired Hi-powers before and if I want to shoot a Broomie I have a second example, which I shoot all the time.
As a collector, I try not to look down my nose at those who own and shoot guns that I wouldn't. Your gun, do whatever you want with it. But please don't criticize me for not shooting mine.