The backglass is actually the upper backglass for a United Corral Shuffle Alley first manufactured by United in October of 1965.
http://www.pinrepair.com/bowl/corral1.jpg http://www.pinrepair.com/bowl/corral2.jpg
Shuffle alleys are also known as "puck" bowlers. Popular in bars/arcades up until about 20 years ago.