That´s in fact a very nice movement, although i´m quite puzzled.
All i can offer at this point is some wild speculating and some hope Marcus, our UN forum moderator, may be able to unravel the history and details of this one based on the movement inscriptions.
These are hard to read on the pictures: Does it say "MB 11 K"? Then i see a number on the main barrel bridge which appears to be 101231?
If you could state the correct numerals, it may be possible to find out a little more.
It does look not unfamiliar in some way, but i can´t find any likely example in the limited material i have at hand.
Based on the pictures, i suspect it´s a thin 11 1/2 ligne movement (around 25.5mm).
The style of the bridges is not unlikely the AS 17xx/18xx/19xx hand wound calibre family
courtesy of Roland Ranfft (www.Bidfun.de)
as is the shape of the pallet lever bridge; the outer specs (11 1/2 ligne and 4mm heigth) of these would roughly match the suspected case dimensions. And the 3-spoke, probably a Glucydur one, is often found in these (albeit a bit different).
But this UN is very different in that it has a different crown wheel, lower cap jewels (the screw-in plates) and 21 jewels (while AS usually came with 17).
Of course the finish is much nicer; these are actually quite fine geneva stripes (they seem to disappear if enlightened from low angles).
The regulator is different from others as well; i´m not really sure, but it may be a Spirofix one.
Over all, this is a fine movement. Regardless the base ebauche, UN spent some serious effort on improvements and decoration.
While the aesthetic finish (mainly the stripes) is quite appealing, the technical finish (polishing of the parts as anchor, escape wheel etc) is probably on par. All this can´t be found in average watches.
And the age is another brain twister:
It may be younger than it appears on the first look.
Although the AS manual wind movements came out in the 1960´s, the only UN movement mentioned until early 1970´s is a NB11QU (the fast beat automatic movement).
A manual wind UN is not mentioned, but i´ve seen others and they certainly exist.
Therefore, i´d expect to find it in the data sheets if it was made before mid 1970´s. But again, all of this is mostly pure speculation and only the numerals on your watch can be verified by the UN archives to do some serious and reliable statements.
So my conclusion, based on what we know so far, would be:
It´s a mid 1970´s fine dress watch by UN with a heavily altered ebauche, probably based on a movement by AS. It´s a nice piece, very dressy and was certainly not cheap in its days.
And to end these ramblings, may i ask you to do the watch a favour?
Apparently the movement is missing the case clamps (the holes at 4 and 11 position on your first picture).
These case clamps attach the movement to the case; because it does have a snap back, the back can´t provide pressure on the movement to hold it in place.
It would be a pity if the nice dial or the movement would be damaged by the movement rattling loose at some point.
I´m sorry not to be more helpful, but i hope Marcus can surface some data.
Thank you for showing the pictures!
Greetings from germany,