Question: Is this an original fingerboard on this '87 Stingray?

So I’m looking for a fretless Stingray and got offered this bass. It looks amazing, serial checks out as a 1987 white ‘Ray, but I’m hesitating. The unlined fretless fingerboard has markers, but only on the upper register (12th fret and up). I’ve never seen that before. Do you guys know if this fingerboard might be non-original?

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