I have been meaning to do a photo comparison between my D 59/66 and my R 59/66A1. There are a few interesting differences. Once the in-laws have gone back to NY, I will get on that.
It's kind of funny, because minutes before reading the OP, I was sitting there looking at the D and considering what it would look like in this lonely ATI Monte stock I have. I am glad I came here, saved me some time.
Hours earlier, I had discovered it doesn't have its original sight leaf, unless they just did part numbers electropenciled on...I was going to ask Jenro84 what his was like, and then I noticed the night sights, which was why I brought it up. I was under the impression that the Ds with night sights would be less common than those that remained original. I sure would like to see them side by side, given mine is only 2k newer...yet original.