Sepp is the 36/40 a field dug buckle? Metal looks a bit grey thats all?
I don't think the EM/NCO 36/40 is ground dug. I think it would have a ton more corrosion on it if it were. I think the dullness is built up patina from 60+ years. There is still quite a bit of grey paint in and round the raised portion of the buckle as well the the reverse. The Grey "speckling" on the buckles face does not appear to be craters when viewed though a 30 loupe. They appear to be discoloration but very similar to the color of the paint in the recesses.