The Bradley-Martin ball mentioned in the article was also referred to in an exhibition at the Museum of the City of New York "Gilded New York" in 2013/14. Among the exhibits was a fancy dress costume by John-Philippe Worth after Velasquez, worn to the Bradley-Martin Ball in 1897.
And there's a cameo portrait of Mrs Bradley-Martin in her costume as Mary Stuart with the ruby bracelets joined as a dog collar and a second ruby diamond cluster necklace as described in the article.