I doubt they are NOS, as when BK2K was made, you bought plastics as a complete set. Slings weren't available separately, and you didn't get 2 sets in a plastic set.
Having said that, I guess there *is* a chance someone bought a NOS set, and used everything but the slings.. a small chance. Would you believe nearly zero chance? :)
A guy named Alan Meyer made repro slings for BK2K and plenty of other games for awhile. His plastics were second to none, the quality was amazing.
As mentioned, there were 2 different sets of BK2K plastics used, depending on where in the run your game was, and I would guess the originals are probably faded, which is why the reds are lighter on the originals than the new ones.
Change them both, and they will look fine :)
