A photo is worth a thousand words 🙂 Many German regimental steins make extensive use of abbreviations that are difficult to translate out of context. “Preuss” would typically be the abbreviation for “Prussian” but it would have a sharp S and not a double S (the funky looking German character that looks like a capital letter B in script). If you can post a photo I can provide more info, because otherwise I am just guessing.
FWIW the Prussian 6th Division was based out of Berlin from 1850 until it was disbanded in 1919. In the years prior to WWI it consisted of four brigades – two infantry, one cavalry, and one field artillery. Each brigade consisted of two regiments. I can provide more info once I see a photo, because otherwise my info won’t be relevant.