Reading the relay and coil table on a Gottlieb schematic
The table on the left of a Gottlieb schematic lists every relay and coil. INDEX gives its grid location (numbers down the side, letters across the top). NO. is its letter code, usually also on a sticker on the relay. COIL is the coil part number to order. TYPE gives the relay style (INTERLOCK means hold type; AG is a different style), CONTACTS the switch count, and USE what it does.
Systems
Source: Repairing Electro-Mechanical (EM) Coin Operated Games to 1978, Part Two, Clay Harrell (pinrepair.com)