Quoted from Otaku:Gottlieb Score-Board is great! (Wasn't sure if you were done yet so waited a little to reply )
I guess I'm an ex-club member, thanks to this game. I sold it a couple months back as it wasn't getting played and so I felt it time to move it on. The middle-pop was definitely my favorite feature on this pin.
Let's see, I got Score-Board back in 2012. I paid $225. Guy I got it from wasn't into pinball, he saw it at a garage sale or something and thought it a worthwhile project to try and salvage something so old but never got to it. I got it non-working (first pin I ever bought that did not play), but the GI would turn on when you plugged it in.
My dad (a retired electrical engineer) and I brought it back to life as a project. Oh, what a mess of a machine. Old solder kept coming loose, and getting all four score reels functional was a bit of a nightmare. Had to replace the plastics on the slings with some custom-draws similar to the original (they were horribly warped and beyond salvage). Probably not the best pure project machine to start with, but we did finally get it going, and I probably learned more on that effort than any other pin.
I took a little bit of video before I sold it to show it working, so I'll share that here to add to the collection of middle-pops in action. While I often play terribly, I will defend myself in this case of having to play one-handed thanks to the camera!