Just going by the book about MFCs. And every box of MFCs I have ever seen. They were all handgathered in the same method they made their opaque types. American Cornelians(Oxbloods), Persian Turquoise, Oriental Jade, Imperial Jade . These all almost always exhibit a nine and a tail just as their Onyx marbles(slags) do. A nine and a tail has been used to describe MFC marbles as long as I can remember and it is one of the more accurate descriptions of a marble companies marbles. I have Cohills book if you want to read it. MFC never made a marble that was not handgathered, unlike CAC Akro and Peltier that eventually stopped handgathering and used gob feeders. I feel my 999 out of 1000 showing the handgathering pattern is not too exaggerated.
I was just using the Akro as an example of things that can happen.