The United States Tricentennial was a series of commemorations and celebrations marking the three centuries preceding the establishment of the United States of America 

as an independent republic in 1776. The American Tricentennial symbol commemorates the occasion.

The United States Tricentennial symbol is one of two commemorative symbols designed by Ron Cobb for the 1979 film Alien,

 both of which were worn as patches and decals by the crew of the USCSS Nostromo.

The US Tricentennial symbol, like the UK-7 symbol, is triangular in shape and commemorates a historical founding event.

The three red and white striped arms in this case represent the three centuries of American independence being commemorated.

The symbol was oriented point down, with the blue five-pointed American star in the center pointing up, according to the Authorized Portfolio of Crew Insignias. 

However, we see in the film that the entire mark has been turned 180 degrees. 

This placed the star in the center, pointing down, in keeping with the flag Cobb designed for the United Americas (established in the year 2104). 

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