Are the holes threaded. Threaded is good.
Take a paperclip, and heat the end of it. See if it will melt the inside surface of the grip. Melting is bad.
If they are threaded, and it doesn't melt they are likely original.
The grip types are pictured at this thread on Jan Still's forum:
http://luger.gunboards.com/showthrea...bakelite+grips
Yours resemble type 5 or 6 grips.
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