It's not a "super duty". "Super Duty" is a Ford trademark that has been used with various products through the years. There are 3 groups of trucks that I know of that have been assigned the title "super duty" through the years-

Medium and Heavy duty Ford trucks from around the '50s-'60s time period.

F-SUPERDUTY trucks from the '80s up to the fall of '97. These were a step up in load rating from F-350s.

All trucks that have the cab that is currently used on F-350s. This would include the vast majority of '99-present F-250s (I believe they made a few '99 light duty F-250s which were based on the platform that the current F-150 is based on), and all '99-present F-350s, F-450s, F-550s, F-650s, and F-750s.