I don't think the OP's confusion was egregious. Reading through this thread, I had some of the same confusion about the source of the glass vs. the source of the cell mountings---it seems that the former is Goerz, the latter B&J, and the shutter mounting is from yet a third source.
So the serial number comes from B&J, and maybe the cell can be dated on that basis. But the absence of an aperture scale on the shutter suggests that B&J didn't do that part; I think you're right that they would have marked it for aperture if it were their doing.
There's nothing too surprising in any of this---mounting a lens in a shutter, assuming the threads are the same, is something absolutely anybody can do. Now, whoever did that, did they get the spacing right between the front and rear cells? The easiest way to find out is to test the lens.