The Coro lotus duettes were commonly unmarked, and this single dress clip, once part of a duette, is no exception. This is one of the best-known Coro designs, and was popular long after the 1939 design patent (attached) was issued. Pale blue enamel with deeper blue accents, a single green leaf, and clear rhinestones on flowers and stems are all in exceptionally pristine condition. Lovely!
Measurements: 1.3 by 1.3 inches (3.3 by 3.3 cm)
Marks: Pat.1852188 on the clip mechanism. This utility patent was issued to Elisha A. Phinney in 1931.
References: The 1939 patent issued to Adolph Katz for this design is attached. The full duette for this design appears on page 55 of Fun Jewelry by Nancy Schiffer.