Imperial German Prussian Model 1889 Officer's Degen or straight sword from about 1889 to about WWI; unusual folding right knuckle-guard (some are without this feature entirely); also an unusual double-fullered blade (both sides). Scabbards are usually black-enameled.
This pattern of sword was used by Bavaria, Prussia, Saxony, amd Wurttemburg - the only basic differences being the Royal Cypher/Heraldic Crest on the guard and perhaps occasional unit inscriptions found etched onto the blade.