What type of buckle is this one...

[phfr]

This one is painted black and is marked B&N-43.

[Ben Evans]

Late war Heer by Berge & Nolte, do you have a better pic of the eagles head?

[lach470]

These are sometimes considered coastal artillery as they were used by them - but also used in much larger numbers by the Heer late in the war. No way of knowing - but like Ben said: most probably a late war heer and not C.Art..
Cheers!

Rob