We could not locate those actual initials, however, after a bit of detective work we feel it could be from the designer Wiwen Nilsson who worked for Jensen Georg Denmark from 1904.
Our reasoning for this, it could be a very early mark when Wiwen Nilsson worked at Jenson at the time. Regarding the Mark G.J.+ W breaking the initials down the G.J is George Jenson and I am assuming the +W could be the designer Wiwen Nilsson. He worked briefly for GJ before opening his own shop in 1927.
If this is the case, this means the jewelry item is very precious and rare, and we are talking thousands! We cannot find any other maker with these initials. Wiwen made 18 CT Jewelry. We are assuming that Wiwen (when he worked for Jenson) thought, I am adding my initial W, as he was also the son of the Court Jeweler to the King of Sweden.
750 mark is 18 CT and apparently he did make 18 CT jewelry.
