To add a few images to Dick's comments.
The first image is a close crop of Aaron Ward (DD-483) and Buchanan (DD-484) building after Federal SB&DD started to modify them to the new standard for eventually two twin 40-mm mounts. Note that the second Torpedo Tube (TT) bank foundation is still in place. As far as we know, this was not removed on these two ships and explains why they have some differences in that area when compared with the sisters that followed at Federal SB&DD.
The second image is a close crop of the same area on Duncan (DD-485). Note that the aft TT bank foundation was not installed. The design change order deleting the second TT bank and 53 mount was implemented on Duncan early enough in her construction so that it was not installed.
I don't have any as completed images of Duncan, but the third image is of her sister Lansdowne (DD-486) and you can compare her with photos and/or the kit of Buchanan to see the differences at the time of completion. There are images on-line of Duncan that shows her early MS-12R camo scheme. But as Dick says, she was repainted to MS-21 by at least October 1942. There are images at Navsource.org and DestroyerHistory.org of this ship and whenever NHC goes back on-line with large images, they have several as well.
The fourth image is an onboard view of Lansdowne. Compare to the fifth image, an onboard view of Aaron Ward. You can see that this area is pretty much in the same configuration.
The sixth and final image is a midships close-up of another sister, Lardner (DD-487), that you can compare to Buchanan.





