New info! A friend-of-a-friend of mine knew a guy...
Anyway: according to his knowledge this should be an Olmo - San Remo out of the eighties,
because of the decals and the cable goes into the frame.

I Googled some more and I came across these:
OLMO San Remo - ********** - ???? which looks pretty similar

Also this decal of the signature looks exactly like the remains of the signature decal:
DSC03189.jpg Photo by brabande | Photobucket

So case closed I guess,
unless you guys have more things to add?