I recently had the good fortune of finding a HUO Gottlieb Rocky. Machine had been in the same house since new. A little cleaning, some new rubbers and it looks amazing, check out how clean the inside of the coin door is, I have never seen one that clean before. The original battery was still on the CPU but fortunately there was no damage and I could easily remove it. Here are pics:
https://www.flickr.com/photos/mike217/albums/72157720171437008
I would click on the first picture then advance one at a time with the arrow. I don't like the way the Flickr home page opens. My game room does not have great lighting so the pictures are a little dark. Enjoy.