Scutcheon?

In Act II, during the radio broadcast, the announcer reads a statement issued by the Governor of Arizona:  "As long as Mantee and his followers are at large a blot of shame will mar the proud scutcheon of these United States ...." (p. 40).

In this case, "scutcheon" takes on the meaning of "proud history" even lending itself to the connotation of "reputation."