As stated before, there are arisaka stocks that had dark brown finish. These are made by very specific arsenals and only in very specific series. The grain of the wood used in stocks such as the one in the original post also come from two very specific arsenals and in only three to four different series. I have some pics of the wood grain and dark brown finish on rifles in my collection I will post a little later. These dark brown finishes and odd wood grain are not uncommon in mid production type 99short rifles. More to come later