I have owned and sold a number of these SS005 pieces over the last few years, some with etched Stuart marks some without. The signed vases seemed to be a bit more substantial, possibly a little heavier and more randomly gilded than those that had no etched mark. I currently have 2 of these unmarked randomly gilded pieces, identical in shape and size to SS005 but strangely 1 vase is not black but is purple. There must be other glass companies making vases in this design. I have only found this variation in the SS005 pattern. Very confusing.