The Regimental Crest of the United States Army Corps of Engineers, which is worn by military personnel.  It is described by the USACE Graphics Standards Manual as:

The regimental crest incorporates all facets of the engineer mission.  The gold turreted castle has been the official symbol of the Corps of Engineers since 1921, although the device has existed since before the Civil War.Scarlet and white are the official colors of the Corps.  Scarlet symbolizes our shared heritage with the Artillery. White, which was the original color of the infantry, symbolizes the Corps secondary mission. The crest is officially worn on the uniforms of USACE military personnel.  Displaying both the Corps castle and the "Essayons" motto (meaning "Let Us Try"), this symbol is a popular graphic used in awards, plaques and other visual presentations.

For more information, see this chapter of the Graphics Standard Manual and this publication.
Converted from CGM version available from a USACE Graphics page (direct file URL here).
U.S. Army