I just found this very old mazzer at a junk dealer.
Burrs are 64mm, so this could be a super jolly.
I'm not sure because the adjustment collar is not the same as in the other jolly I've seen.
Maybe the older version?
It is not a stepless mechanism: the ring has lots of holes in its lower part, and the small pin you can see from the photo locks the rotation slipping into them.

well, I bought this piece of junk just to reuse its adjustment mechanism.
I'm planning to build a sort of manual grinder.
For this reason I need to remove both the adjustment threaded collar and the outer threaded part attached on the body of the grinder.
It seems to me that the latter is a separate piece from the body, so it should be possible to remove it.
Any idea on what should I do?
alberto

Does it say Mazzer on it? There are a lot of manufacturers of 64mm grinders of similar design.

Any idea on what should I do?

Fix it up to look new, and then buy a pharos or an HG-one. Seriously. It looks like it could be a real museum piece. You can buy adjustment collars for mazzers online.

We have the same grinder at café as a "spare one". It definitely is a Mazzer.

Actually I can't find Mazzer logo on it.
But some particular are definitively Mazzer.
For example the heavy bottom and feet.
It also has doser (already removed in photo).

Plus the OP is in Italy. That might make it more likely too.

Ours have Mazzer Luigi sticker on the back.

Definitively a first generation Mazzer Super Jolly (from the 70s), check here. Your sticker is certainly gone, that's all.
I'm pretty sure that the lower part of the "adjustment mechanism" is part of the grinder body, you won't be able to detach it unless you cut the metal... but you will completely loose the alignment doing so.