AE 40 Monophone (Year of mfg?)

[ma_xyz]

Just cleaned an AE40 (my first and only one, got it on eBay).
A very nice instrument. I like the complex and heavy setup. Also the very expensive/complex hookswitch mechanism. Must have been a very expensive phone in it's time.
I also like how it sits even on a table if put on its head, easier to open the screws :-) once open though I thinks it is not very service friendly.

Is there any known possibility to identify the year of mfg? I did not find any date markings.
According to some posts I read these were made from 1940 to 1954?

Bottom Ids (see also pictures): N4074 E0 RN7

It was only a little dirty, the bottom gasket is dry but does not (yet) fall apart, everything else OK. Audio, ringing and dialling is working. But dial is not working very well, gets stuck sometimes, will disassemble it again and trying to fix it.
It had a black plastic handset cord, probably original, replaced it with a cloth covered black cord.