First, look for the name plate/ID tag. Get the mfg. name and model or cut number.
Next, check the overall condition of the pump. Dents, holes, obvious missing pieces. Then step back and look at the pump. Observe the style or design. Is it basic or a pleasing design? Is it boxy or art deco? Note the overall height, width and depth of the pump.
Get back to us with that info and maybe someone can give you an idea. The right model pump is worth a good bit depending on condition. Even basic pumps in good shape can be a good find.