Hello,
I have a copy of the Mauser archives book in front of me, from what you`ve described you have a Type L "Special African Rifle", if it`s in 8mm Mauser it`s certainly pre-war as the treaty of Versaille (1922) forbade manufacture of sporting rifles in military caliber. Unfortunately I cannot find serial number lists in this book, only detailed descriptions of characteristics. Also lots of pictures....
I`ll be happy to help with what I have, there is alot of information here, but again no serial numbers that I can see.