It looks to me like they may have replaced the chain only.
Sprocket teeth and idlers appear to be older.
As I understand it, System One was designed to wear out as a complete set, meaning the sprockets, idlers, rollers, and chain all wore out at about the same time. This held true for the non LGP units we had.
I see the one listed is an LGP so it's possible they ran it on rock and the chain wore out prematurely.