Certain guns just seem to have 'it', whatever 'it' is. I guess a combination of perfect barrel making, actioning, file up, stocking, engraving and finishing. When you combine all this with unmolested patina you have a great gun and this Boss & Co. 12g over and under is such a gun.
Part of the reason that it has probably remained in such nice condition is that it is a left hand opening gun. Even left handed people don't know how to use a left hand opening gun it seems nowadays, they have adapted to using right handed ones. So with no demand it seems a perfect reason to keep it in the safe and enjoy it!
A nice reference for any budding engravers who seem these days to race past the basics and try to go to the game scenes and carving too quickly. Rose and scroll such as this is timeless and so few people can actually do it any more to a standard such as this. Click on the photo to enlarge it.