Black mining cap badge?

[Ser-g]

hi folks,

i started expanding my collection of visor cap's into the civil organizations.:thumbsup

i just got my first mining ministries in.:)
it is a 1984 summer supervisor cap.
the very weird thing i find is that the badge doesn't have a blue backing but a black (dark greenish) one.:confused:
the buttons are unlike any i have seen too, plastic back and copper like front (with right mining embossed emblem).

is there any thing you could tell me about this?
is it a reproduction?
does is has a slightly different significance ?:idea

pictures are borrowed from undertheredstar.com.
my cap is exactly the one in the picture.