Hi Corazone, congrats on your 191U! As the previous poster stated, it was made at Singer's Utsunomiya factory in Japan, hence the "U" after the model number.
The 191 is based on the internals of the model 15, except the tension assembly is more conveniently placed facing the operator. You'll find it has the same vertical hook arrangement as the 15's.
The 191's came in both potted motor and belted motor configurations. I think I see a hint of a belt in your photo but it could be something else in the background.
The knob below the model # badge ought to drop the feed dogs.
The 191 I've got is a 191M (Monza, Italy) and I know there's a 191B (Bonnieres, France). They're all exactly the same, except for the potted or belted motor.
In the '70s or '80s Singer also made an industrial model, totally different from ours, that they gave the 191 model number to. That may turn up in your Google searches and cause a bit of confusion.