my thouht it is a cleaned ground dug with partial havy rust .
I'm searching for
special SA/NSKK/NSFK with maker marks
Link to my collection : http://www.warrelics.eu/forum/album.php?albumid=1175
I am with Markus, looks like it has been partially in the ground
I think the buckle is not from the earth, would be a different overall look.
Rather, the attic and one side hit the damp.