Many thanks for all your warm words!
There's no great story behind it. A friend of mine found it on a WWII battle field by himself. He had some effort to recover the buckle within all the roots. Fortunately he didn't remove the main root wich grew through the buckle within all the years. In the end I was lucky enough to get the buckle from him.
And yes, it fits perfectly into a standard Riker mount!
Fantastic my friend what a find