My rugby pictured came from Europe. So, as is the case with a lot of RL, I'm going to guess that there were subtle differences between the US and overseas version(s).
On the issue of the boxed "Ralph Lauren 1967" vs the horizontal borders extending to the edge of the plate with no vertical sides to the box, that style of plate is also used on a number of the other Stadium pieces - the royal/navy split hoody and the red/navy split sweatshirt with the plate on the back (which might have been a primarily Japanese release, but I could be wrong). So, the plate itself is not uncommon and certainly consistent with plates used within the line. ...Obviously other items used a horizontal band like that vs. a box too, but the format wasn't exactly the same, as the band was colored (Paper jackets, p-wing Stadium tees).
So, my guess is international vs. US versions.
Of course, the best person to probably answer this would be Jay.