looks like your decal sheet is for one of the 1963 Sebring 12 hr. entries by Shelby American. "Slash" type striping would often be used, and with different colors, across fenders or the nose of a car to help the pits identify who it is coming in when a team had multiple entries. As to who, where and on what car, I'm certainly no expert (unless I'm building that particular one). Leave this to the guys who can tell you what the chassis number was, the displacement and "tweaks" for that engine, etc. etc.