Hi Bill,
To find a period photograph of an item 4mm in diameter is perhaps like looking for a 'needle in a haystack' but I admire your persistance in answering the question.
The trouble is I think during this late war period you may come across differences in these connecting pins, depending on the manufacturer. At the end of the day its purpose was to make sure that an electrical wire was firmly connected to form a circuit, in an almost 'foolproof' way.
Now I'm no expert in this area but looking through your thread it appears that the pin is fitted within the wooden 'protector block' It also appears that this wooden block acted as a handle for inserting the pin (is this correct? - not just for protecting the plug from damage). If this is the case then the end to which the wire is connected will be within the wooden block (the flat end you refer to) - this makes sense as it would protect it from damage.
The end which is inserted to make the connection appears in your photos to have two methods of securing it into the socket. The first a 'spring wire' and the second a 'splayed slot' - both to me would seem to 'lock' the pin into place reasonably well - this was after all crutial to the firing of the rocket. So I think you are looking at two different methods of construction, the slotted version being a simpler manufacture process.
The rear end of the connector looks like a standard electrical fitting - I am sure I have seen this on other electrical items, but for the life of me I cannot think what at present to show a photograph.
I am not sure if the wooden block pulls away once the pin is inserted into the connector - held in place by the tension of the connector - maybe you know the answer to this?
anyway a couple of photos you already posted with my 'thoughts'. This is just me thinking aloud though, and running ideas past everyone for discussion, I have no proof of anything - only suggestions.

Ok, I found an example of a pin, its not the one I was thinking of but serves the same purpose - electrical contact. This one forms part of a two pin plug for a WW2 Bomb Release switch, so of the period. In this case the pin is part of a bakerlite holder, the wire is inserted into a hole within the pin and soldered in place.
Having found this example, I wonder if there are other 'similar' applications of electrical wiring in German 'period' items which may shed more light into the connector you are looking for? There certainly must be other items that require a similar pin connector?
Kev


