It is an original crystal IMO.
On 1965-67 productions the 165.024 came with a black rehaut, not a silver one.
Yours is properly an 165.024-64 reference (65 or 66 production), so would be ok. Most crystals on these have been replaced (service/replacement crystals have silver rehaut, also most old service ones), so black ons are pretty rare to see. Better pictures /close-ups should confirm that. I would only polish the crystal and not replace it, unless it is cracked and can't hold any pressure. And even so, save the old part.
Even without movement and caseback shot, I dare say that you have a nice and all original 165.024-64. Congrats.
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