The Sport had a few rolling changes before the Sport 2 came out.
The very first Sport came with the 1:8 5R barrel, and a M16A2 style rear sight that was like a chopped carry handle. Similar to this.
Then they changed from the above rear sight to a Magpul MBUS folding rear sight.
And finally, the last change to the Sport changed from the 1:8 5R barrel to the 1:9 barrel that is currently on the Sport 2. The difference between the Sport 2 and the last version of the Sport was the addition of the ejection port cover and the forward assist.