I wouldn't give the writing inside the grips much thought.. Just that the grips might come from a pre 1923 Luger, that is ..if the writing is not faked for some reason.
If a name and 1923 date where found on a piece of paper followed by ' Two milk, one bread and a bottle of rum'. It would not increase the value of the paper any more than the same writing on a pair of Luger grips. Unless there is some story behind the writing, it's just 84 year old writing.. At least in my eyes ..and probably many egyptians
You are lucky to have a nicely restored Luger in good condition, congratulations with it!