No comment on the wasted "ming"... get some sleep, Joy.

I used to work in the coal industry. It was widely mechanized (mechanised for you UK folks) starting around 1880. The first mechanical scoop was sold in the 1860s. The unioniz(s?)ation effort didn't really take hold (in the US at least) until much later.
The juxtaposition of manual mining imagery with the more modern language and the union references makes me suppose that it was an older song that got re-tooled into a union recruiting song.
I don't know any specifics about the song, just throwing some historical dates together and drawing some very shaky conclusions.

Oh, and it definitely doesn't sound like an American miners' song. I don't recall ever hearing anyone in a US mine refer to "dirt and muck", for one example, nor use the term "bloody." Again, just an impression; maybe it will help place it (or at least rule out some unlikely possibilities).

-Glenn