This is an interesting Duette rhinestone brooch made in Canada by Coro in the art deco style.  The mechanism is stamped “Made in Canada”, “Patented 1935” and “Pat. 1852188”.  The piece is unsigned, but this was made by the Coro operations in Canada - I have seen this exact model, made in the US, signed Coro.  The patent number 1852188 was filed in 1931 by Elisha A. Phinney of South Attleboro, Mass. for the George H Fuller & Son company of Pawtucket, Rhode Island for a brooch clasp.  In 1933, however, Coro  was granted the patent for the Duette mechanism, and then was granted an improvement patent in 1934, producing the first Duette clip brooches in 1935.  As they were the first, and were very successful, others started inventing their own mechanisms. 

This Duette brooch measures 3 1/2” in width and each clip measures 1 3/4” in width and 1 1/2” in height is in very good condition with no noted missing rhinestones - there are some “dark” stones and there is one area of the stamping on one clip with there are no rhinestones, but there doesn’t appear to be an indent in the setting, even though there are rhinestones on the opposite clip (see last 2 close-up photos).  Very minor consideration, as you really don’t see this under normal viewing.  The mechanism is in very good working condition.

This is a rather rare example of Canadian Coro manufacturing - great addition to a collection!