Unit identification

Received a double date 1915/1920 DWM for Xmas. Right side of breach shows to be military issue. Eagle on trigger housing, 1999 serial #,Gesighert on safety, strawed grips etc. X'd out markings on grip are S.L.Po1.2628 are what I'm trying to get help identifying. It has other marking on grip of S.P. over C. I believe this to be Schutzpolizei, District of Saxony, city of Chemnitz. If anybody can help it would be appreciated. Been to two gun shops, book stores, and two public libraries and am geting frustrated.