There is actually 2 different versions of the BK2000 plastics, incl slingshot plastics.

The original prototype plastics went on the first run of the BK2000 games, and then about a quarter of the way along, they changed plastics to a more lighter/modern colour theme/style. Some plastics stayed the same, and about a third of them changed completely/alot.

What u have got is fine, its not wrong, just a set of each by the looks of it. If i saw the rest of your machine, I would know which full set u had, but either way, or either set is fine.