I can't help with attribution but I like it. Over five KG is huge. It looks like a mini Anish Kapoor sculpture. A really interesting thing. The technique was popular at the turn of the century but this shape looks more 1960's, 1970's to present. I can see why attribution is a bit tricky. I hope someone has some recollection of this kind of piece- it would be hard to forget seeing it really... Good luck!
Robert (bOBA)