James Willing of the Spooky Pinball Podcast's EM Dungeon segment (http://spookypinball.com/podcast) comes on to fill in my knowledge gaps on bowling games and their special modes and features, including ball bowlers and shuffle / puck bowlers.
Jim put up some photos of the United Skippy machine's glass on the EM Dungeon Facebook page (https://www.facebook.com/emdungeon), which I will reshare on my Facebook as well. https://www.facebook.com/foramusementonlypodcast