Mysterious LK stamp

Im just going on a train of thought, could the LK stamp be for LeihKraft, or LeihKräfte ="Loan arms". Perhaps rifles that were "given" to allies of the Germans? I know that there really isn't anyway to be certain.

LeihKraft is problematic , because Kraft is Mannpower or Power not arms. Leih in that is used mostly only as leihen or loan but not as designation.