I posted earlier today about how I remembered my cousin knowing someone whose family owned non-production machines from Stern. At the time, I said that I didn't remember them having the Junji Ito machine. That's still true, but afterwards I decided to call up my cousin and see if she remembered her boyfriend telling her anything about how his dad got the machines, so I could get more details, and the subject of these forums came up. I told her abit about the Ito machine, and she said it actually sounded familiar to her. Aparently, for a bit over a month, boyfriend's dad had a machine that was always under a tarp. My cousin says she asked the boyfriend about it, because of the tarp, and BF said his dad's coworker had given him as a gift. (Because he collected unreleased machines?) She also remembers that they kept it unplugged, unlike their other machines. Because it would make weird noises and scare the family pets in the middle of the night if left powered, apparently. 

She says she took a peek under the tarp just one time, and couldn't make out much because the graphics blended into the shadows (makes sense if they were black and white), but she does remember the rails the ball rides on looking like they were covered in something, though she wasn't sure what it was supposed to be. This is from her hazy recollection, but she remembers it looking dark and stringy, and seems to think it was either supposed to be moss or hair. From what she remembers, the machine didn't stay around for long before the dad got rid of it, but she didn't think it was important enough to ask about.

Does that sound like the Junji Ito machine? If so, it could still be around somewhere.

EDIT: Reviewing my own information, it's possible this isn't another machine, but one of the others already known? Unlike the other cabinets their family owned, the covered machine was not one the father personally acquired from Stern, but one gifted to him by a coworker. It could have been purchased under the same policy as the ones he bought from the company for himself, or they might have gotten hold of one of the existing cabinets from somewhere else for his collection of rare machines. If it was one of the Junji Ito machines at all.

As we aren't really sure WHERE the 3 machine + prototype are, it's absolutely possible that it's one of them,but equally possible that it's a fifth one we never heard about 

Can you tell us in what years the machine was at her home, and in which state of the United States did his father live, and ideally, in which state did the machine end up (or at least a clue about the buyer?), unless he threw it in a landfill?

This was when our family was still living in Illinois. The machine was not at my cousin's home, but her boyfriend's. As I said in my other post, the boyfriend's father worked for Stern, who apparently make cabinets that aren't in production available to employees, though I don't know the details on that. Just that her boyfriend boasted about the fact. This was all around twenty years ago, so both my cousin and I are going off of our memories. She told me when I talked to her that the cabinet being kept covered and unplugged was odd enough for her to be curious, but it didn't seem important. She remembers it was there for a while, and then it was gone, but never asked about where it went. I could try having her get in touch with the boyfriend, but they haven't been together for quite a few years, and honestly I don't even know if she would still have his contact information.