Well, not to piss on your party Steve, there are 2-3 main variations, and I think the two above are postwar, all of mine, and the ones Arnaud made some replica's off, have the ridge where the HT cable goes in.
Another difference is the knurled special nut that was used on the older ones, see picture. (this is a US thread, not normal)
I think you can also see the details on the factory shots, will have a look.
Lex