Based on the age, it's quite probable that the fretboard is Brazilian RW, not Indian. this can make quite a difference when trying to match woods. What about designing a nice pearl ( or other) inlay to cover the area in question? another option - although much harder to do - would be to slice a thin veneer off the underside of the fretboard extension, and use this as your filler piece. You could then replace the wood where you removed the veneer with something similar, w/o so much worry over it matching.
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---Tom H ---
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