EM schematic symbols
Two parallel lines are a normally open switch; with a diagonal across them, normally closed; an open and a closed pair sharing an arrow is make/break. A curly pigtail is a coil or relay, and a short pigtail in a circle is a lamp. Williams and Bally sometimes mark score motor contacts with a dot in a circle.
Systems
Source: Repairing Electro-Mechanical (EM) Coin Operated Games to 1978, Part Two, Clay Harrell (pinrepair.com)