So called "WW1 French Medal" for $3.00 is really rare Oldenburg decoration

I knew this was a German decoration (unknown State, date, or name). I bought it for $3.00 (see original tag). It turned out to be a House Order of Duke Peter Friedrich Ludwig (Oldenburg) Honour Cross 3rd Class with swords awarded 1856-1918. I was told that there were fewer than 600 awarded between 1856 and 1918. I was also told the current value is 300 euro ($425.00 US). I am keeping it for now, and will complete the repair to the sword hilt handles (already started) and the ribbon mounting process. One really nice Pick! Cheers Captain Albert, Army Field Historian for the California Center for Military History, Naval Research and Study Element.