1901 - mid 1990's

In 1901 Carl Rosenberger and Emanuel Cohn created Coro Inc. in New York City. They initially operated under the name Cohn & Rosenberger until 1943 when they changed the name to Coro, Inc. (CO for Cohn, RO for Rosenberger).
The American division of Coro went of business in 1979. The Canadian division produced up until the mid 90's.
Marks
Coro used many different marks throughout it's long history. The earliest pieces were marked CR. Here are a some others:
Coro" script mark which was used first in 1919

Coro-Craft Sterling (after 1942 to 1944),
Coro Pegasus (after WWII).
Other marks used:
Coro Craft (used after 1937),
Sterling Craft Coro (1942)
Coro Sterling (after WWII),
Corocraft (used after 1944 to 1947),
Coro Designers
Important Designers in the history of the Coro Company were Adolf Katz, Gene Verecchio, (1933 - 1963), Robert Geissman, (1938), Massa Raimond and Oscar Placco, (1938 - 1945).
Most Collectible

Gold washed sterling vermeil pieces, made in the 1940's are highly prized by collectors.
One of the most popular pieces of jewelry that Coro
produced was the duette double clip, which could be worn separately or
could be combined
into one brooch. These duette clips are likewise popular with
collectors today.
Coro's Figural "Jelly belly" jewelry is highly sought after and also commands a premium price.
Dating

Prior to 1955 the Coro company was know for registering their designs with the US patent office. Most, but not all, were registered by Coro's most prominent designer Adolf Katz. A perusal of the patents registered is often a useful way of dating some of the older Coro Jewelry.
Antique Jewelry Research Information