I usually figure those to be 1930s. I've got some I still use in my basement tool box. Just looked and I don't have a 5/8", so if you want to trade them for something else, PM me.
The 1940s Blue Point I have are semi-polished shanks, full-polished ends.
Late 1940s, the same wrenches were stamped Snap-on and the deceased tech from whom I got the Blue Point had some warrantied, replaced by a Snap-on, which is why I don't have the complete set.
jack vines