An interesting pair of grips that are likely late war and, therefore, would have been used on a Walther P.38.  This is another example of the attempt by the Germans to stretch their supply of bakelite by adding filler to the matrix.  In these pictures it looks like the filler might have been placed in the mold before the bakelite because the filler is most prominent in the mold grooves.  Also, you can see very little filler on the inside of the grips.  I have no experience with this process so I could very well be wrong.  In the last picture you can really see the fiber in the filler material.