The letters on your modern car’s trunk lid might have no real meaning, but the “S” on the back of a classic Porsche 911 signified a major performance upgrade over the standard car. Porsche’s marketing for the original 911S cautioned, “This is no car for a novice.” The 911S rewarded skilled drivers while being known to put a scare into those unfamiliar with its handling traits. RM Sotheby’s is offering a rare concours-restored 1968 911S at no reserve at its Amelia Island auction in March. Expect hot bidding.