Founded in 1923 by Igor Sikorsky in Long Island, NY. Currently part of United Technologies.
Note the differences in the outer edge decoration as well as the subtle changes in the wing emblem.
11 - Five year pin.
12 - Ten year pin with green stones.
13 - Fifteen year pin with red stones.
21 - Fifteen year pin variation.
22 - Twenty year pin with pearls.
23 - Unknown year pin with new (current?) emblem.
24 - Unknown year pin with new emblem and blue stone.
Sikorsky was a division of Vought from 1939 to 1943. The F4U Corsair was made by Vought-Sikorsky.
Note the similarity of many of the above to an early Vought service pin.
Five year Sikorsky pin showing the reverse.
What Aerofiles.com has to say about Sikorsky.
Sikorsky homepage, and their history.
Igor Sikorsky Historical Archives.