This is a gorgeous vintage Retro Moderne mid-20th century brooch. Marked "Sterling" and "Sceptron" on the reverse. Two rows of small white rhinestones mark the bow's knot, while larger blue rhinestones line the inner bow. A very dimensional pin, it measures 2.5" across, 1.5" high, and domes out to nearly half an inch. In very good to excellent condition - a bit of patina, which I've only lightly cleaned.
"Sceptron" was a mark of the Reinad jewelry company, and was first used in 1944. Accordingly, this pin dates from the later 1940s, perhaps the early 1950s.
Book reference: "Collecting Costume Jewelry 202" by Julia C. Carroll, p. 439.