I have been stumbling along with trying to fill out this set. Circa 1948-1953, New Britain, NDF, but you will find most all NB wrenches are NDF prefixed. I started out with two some years ago, and now have most a set of combination box/open. Along the way and thru some of the guys here have also acquired the combination open ends, combination box ends, combination box end offset, and the thin tappet wrenches. Just discovered there were also combination box end very short. Am missing some sizes in these combination box/open, 3/8, 13/16, and anything above an inch. The five or six on the bay right now are all sizes I have. In the late 30s there was a similar style marketed with a single raised bar, and gotten over a dozen of this style. Got them out in the shop right now, and baby it is cold outside! If someone has one of either of these styles, I will bundle up and go check. Let's see, also have a collection of S wrenches, a few Barcalo, and some Kraeuters, of the diamond K design. Did I mention my set of 1947 Craftsman?