Blue Glass Silver Swirl Design Nordic Brooch and similar items

So we found instances that this may be sterling silver and Nordic in origin but we can?t find marks to justify it. We are including a photo from a website with the exact same brooch that attributes it to Frederick Bieberbach a German jeweler who lived from 1877-1954 and worked for 23 years as the head designer at ?Henry Blank and Company? located in New Jersey (from 1912 to 1935). Active from the 1890s until late 1940s, Newark firm of Blank was one of the largest and most successful companies producing jewelry and women?s jeweled wristwatches, pendants, chatelaines, as well as men?s wrist- and pocket watches. According to Official Gazette of the United States Patent Office, Bieberbach invented original ornamental designs in 1945. Traditionally, he used gold vermeil finish, sterling silver with art glass imitating emeralds, sapphire and ruby, and rhinestones. Signed on the reverse ?sterling by Nordic?, or ?Nordic Sterling?, most designs include Art Deco style ? swirls, ribbons, bows and floral spray brooches and pins.? We have been unable to find the STERLING BY NORDIC? but we do note remnants of gold overlay which would be consistent with his work. Missing some small rhinestones. See last photo and use Google Lens to find the website. Will ship USPS with tracking to winning buyer