Probably to drive a pump using the drive shaft as the source of power.

Terrell Machine Company - History

Check the author notes, the company was bought out and rolled into Comer Industries in '92.

I find a lot of similar equipment, but can't find a hit using the model number in your pics.

Not sure what you would ever use it for. Since you don't have whatever those belts were driving.... Given the age and the facts surrounding equipment like this, I'd say it's probably headed to the scrap heap.