Age has a difference too, as Sig has changed fonts over time, in this case they are both P229-1 Barrels, and you are correct, as the Barrel on the right appears to be cut for a LCI. Even the "finish" has changed over time, while your Legion Barrel may have had a PVD finish similar to the Legion's finish, other models wouldn't necessarily have had it. Some vintages had DLC finishes which would hold up to wear, very well over time, but likely cost a little more, than Sig determined was really needed.