Well, 135mm or 13,5cm is the standard focal length for 9x12 film as it was used for a long time. Sometimes there are 12cm or 15cm lenses but mostly it is 13,5cm.
The back may have been coming from a Nagel camera but the camera can be anything, some small shops even built them themselves and just bought bellows, lens and shutter.
Some backs and screen holders are interchangeable, there are certain types of folds, "Falz" in German (meaning a fold (noun)), so you could use and / or buy additional film cassettes
which didn't have to be branded by the maker of you camera (and thus were cheaper).
The Tessar is a very good lens, even so today, back then it was the best you could get, on par with a Heliar which is a five lens design.
But then a Heliar was much more expensive.
So it could be anything, sometimes there is a name on the front door, at the bottom between the rails, sometimes there is something printed in the hand strap.
Maybe you can find something there but judging from the shutter, it was built after 1908 roughly, before that it was compounds, later ring set compurs.
Maybe the twenties? A serial number would help.
regards