Artifacts from the family of Col. Harland Sanders contained fried chicken recipes, but KFC has insisted the one with the correct 11 herbs and spices is kept secure in its headquarters.

KFC’s “Original Recipe” trademark, which it says is a secret blend of 11 herbs and spices, has long been part of the company’s branding. The blend is closely guarded, and the company calls it one of the most “iconic trade secrets in the food industry.” It first trademarked the phrase in 1984.

In a lawsuit filed Nov. 8 in the U.S. District Court for the Eastern District of Texas, KFC has accused fellow fast-food fried chicken purveyor Church's Texas Chicken of violating its trademark rights by using the phrase "Original Recipe" in its advertisements and promotions.