I have a New Model Blackhawk, that I bought new, in 1983. The box it came in has January 1978 on the back, BUT that might be the date of the printed label (with all the patents) and not the actual date of the box itself.
the Manual does not have a date I can find, but does have the number "MRN 11/40/7-80" on the cover. This might mean the manual is from 7/80, but I don't know.
Also have a super Single Six, also bought new, and in a Ruger box, sorry I don't recall the age of it, but the box says April 1991, and has many more patent #s than the 78 box.
Here's another point to consider, the cardboard boxes were NOT numbered to the guns, and while I know my 83 Blackhawk came in its original box, I also believe that the Single Six probably did not. The dealer went into the back, and came back with a "ruger" box that it fit in, one much larger than the pistol. SO, it is entirely possible that a gun& box could be all "original" in your hands, but not the same as was shipped from the factory.
Hope this helps.