Looking for a maker for my Silver ball necklace

Hi I’d like to find out the maker for my lovely silver bead necklace that I picked up from the charity shop. It’s a modern necklace judging by the clasp and is in a style very similar to one sold by Tiffanys although unfortunately I don’t believe it is one of theirs.

It has some tiny markings that I managed to pic out in my microscope - CU in very plain lettering in an oval. 925 surrounded by scales, and a square with what appears to be some sort of castle. It also appears to have an intricate chain on the inside.

Any help would be much appreciated.
Kind regards

It’s difficult to tell from your picture but the castle may be the mark of the Edinburgh Assay Office (EAO). 925 is obviously the silver standard and the 925 and scales mark is called a Convention Mark - it is a (mainly) European standard mark which was introduced in the 1970s but did not come into regular use until the mid 1990s. Assuming it is an Edinburgh mark the lack of a date letter suggests a post-2000 date. The maker / sponsor CU is not listed on the EAO web site so I cannot suggest a name.