There has been a bit of water under the bridge since my last post.
The MV tool specialists have come to the consensus that, as Plumb owned P&C tools, it probably had them originally in the box.
It is, apparently, a Plumb model 9990 box. It appears in the 1948 P&C catalogue, I'm told.
My realistic chance of assembling a P&C kit is a number approaching zero
. As I have, in my ignorance, already started on a period-correct Craftsman set, I'll continue. Note that the TM picture is indicative only, and there is a real chance that the box could have been filled by whatever brand was available at the time, or even a mixture of brands. Times were pressing!
Further, and some comments here are welcome, I'm told that there were no Craftsman-branded 3/4"dr. sockets in WW2, but that the circle K stuff (made by SK) is post war. So a suitable 'bedfellow' in a kit of Craftsman would be SK branded 3/4"dr. sockets.
What do you think?
Then, how do I identify that SK tools are WW2/1940s', and not pre- or post-war?
Yes, it is not perfect, but will have to do in the medium term.
Hope this helps.
Have a nice day.