I don't collect black glass per se, but I do have two examples in my collection now. One is an 1875 labeled ale featuring some milkiness in it, and the other is an onion with an amber swirl wrapping around it two and a half times which I'll post in its own thread later.
Great onion, Robby! According to Van den Bossche, these were mostly made in Belgium and Germany for the Dutch market. I understand that the flat-sided, bright green examples came from Germany. My specimen has ripples and adhesions on the surface, though the lip is precisely finished.