Final answer:
The information that must be legible on the nameplate of an LP-gas container constructed before September 1, 1984, includes the contents of the container, manufacturer/distributor details, serial/identification number, water capacity, and owner details (if applicable).
Step-by-step explanation:
The information that must be legible on the nameplate of an LP-gas container constructed before September 1, 1984, includes:
- The contents of the container, such as the specific type of LP-gas or combination of gases.
 - The name and address of the container manufacturer or distributor.
 - The serial or identification number of the container.
 - The water capacity of the container.
 - The name and address of the container owner, if different from the manufacturer or distributor.
 
These details provide important information for proper identification and handling of the LP-gas container.