An arcade "monitor" consists of
- Open metal frame
- Picture tube (CRT)
- Deflection yoke
- Aquadag grounding strap
- (optionally) external metal purity shield (very early versions of the G07/K4600 used these as they wern't baked into the RCA tubes themselves)
- Chassis (main circuit board plus neckboard) and associated wiring
Its the PCB of the monitor. Contains all the capacitors, the flyback, fuses etc for the monitor. It also is what the power and video signals plug into.