1976 Valiant, weight attached to rear floor.

I have a weight that was attached to the bottom of the rear floor.
I really don't know it's purpose. This car was a 318 with a catalytic
converter. This was mounted on the right side of the car and may have
been used to counter act the weight of the exhaust system on the left
side of the car. If anybody wants it, just pay $12.00 for flat rate shipping
from El Dorado Hills, Ca. Other wise it's off to the scrapper. I would be interested with any input as to it's purpose.