Also wanted to add that Christoph Funk circa 1933 offered a Leicht Stahl Drilling but his light weight alloy was sourced from Siemens-Martin/Martin-Siemens as Siemens Martin Spezial Einsatzstahl. I think it some sort of diffusion/infusion process similar to electro-plating/melting. If I'm not mistaken it was the basis for the Jubiläums Drilling 1835-1935.

Kind Regards,

Raimey
rse