"X" Suffix - The letter X was used on three separate occasions. In the early 1960s it was used on the box next to the model number which indicated the box included "eXtra" accessories along with the standard reel. The reel did not indicate the letter X on its body. The next time the X was used was in the late 1990s. It was incorporated directly on the reel as part of the model number. The last time this letter was used was in 2001 to indicate the (new) Mitchell 300X and 300X Pro.
