P-08 with aluminum grips

I was offered recently a P-08 Commercial (1923?) with aluminum grips. Serial number is in the 77,500 range, cal. .30, C/N proof mark, "Germany" under barrel, "Gesichert" under safety lever. Apparently this Luger has retained its original rust blue finish (it is white inside)and straw but unfortunately it has a S/42 toggle with mismatch military style numbers. Grips are identical to DWM wooden style grips except they are aluminum. If I recall well, Walther manufactured PPKs with aluminum grips during WWII. Could this Luger be a WWII rework? I doubt Germans ever used P-08 in 30 cal. as service pistols but who knows? A post war refinished one?

Any information about this variation and more specifically about the aluminum grips origin will be greatly appreciated. Thanks.