Ok, I've watched that above video about ten times. I think that seat is a re-make. On the upper seat back there is basically four holes on the right (as your looking from the back), and three on the left. Of the four holes, the one to the top center of the seat should be about a half inch smaller in diameter. It's not, it's the same as all of the surrounding belled holes. Also, refering to the four hole cluster, the top right hole looks to be too far out away from the center of the seat. The wired edge is a little too rounded too. It should be more angular. ...Nice seat, looks close, but not the way they were. ...Scratch that one as a seat referance.
You can refer back to page 3 for Spinpachi's blue print. Refer to 1:30 in on the video for comparison of the holes, 3:19 for the wired edge.