I actually had in mind to send Struer Museum an email, to see, if they could shed some light on these early models.
There is something really strange about this. You could very easily be tempted to think, that the '1' on the black 4401 indicates, that it is a prototype, like on the others we have seen (Silver 4401, 6001), but that isn't the case according to the service manual.
The silver 4401 must then be an early sample on the same level as the 6001. And the black 4401's we then know of, are on the same level as well, as they have red labels. The confusion lies in, that the red labelled black 4401's aren't named different from the black production line 4401's mentioned in the service manual, but that the silver one is...
I will try to contact Struer Museum at some point, and send them the pictures from this thread together with our speculations, if the copyright owners of the pictures give me their permission.
- Dennis π