Some did, but not all.
NR Davis and Sons operated from 1893 to 1917. Is that close enough?
The value of a 12 gauge NR Davis and Son single shot shotgun actually depends on a couple different things. The condition and age of the shotgun would be highly important in determining the value.
One model was Diana.
There isn't going to be any, unless you find an old catalog. The NR Davis Gun Co bought the Warner Gun Co in 1917 and began producing guns marked Davis Warner Arms Co. Shortly after, the Crescent Firearms Co bought the company and produced guns under that name from parts already manufactured, until Crescent was bought by Stevens Arms.
the internet
50-125 or so
I have a Davis & Sons, Davis Warner Arms Corp, side by side 12ga In fair condition and it is valued at $200.00. In excellent condition it would be worth about $295.
0-150 USD depending on exact configuration, age, condition, accessories, etc..
Wall hanger to 125 USD or so
Well, very few collectors are looking for an NR Davis hammerless, so unless it is in excellent condition (and you wouldn't be thinking of refinishing it if it was in excellent condition) it won't be worth more than a couple hundred dollars. As a usable hunting shotgun, any good double should be worth about that much, too. Of course, for just a few dollars more you can buy a new shotgun with a manufacturer's guarantee. Parts will be a problem if you ever need repairs since these guns haven't been made for 90 years.
No, there is no such element Nr
NR class was created in 1996.