Although Saltasaurus was a huge animal, it was still pretty small for a sauropd, standing perhaps 3m tall at the shoulder and weighing around 8 tons. Vast nesting sites have been found in Argentina and Spain, with pieces of shell strewn across wide areas. It looks like many hundreds of individuals had laid their eggs in the same site over a long period of time.
The piece you'll get will be about 3.5cm across. It's a pale grey, with a distinctive dimpled texture, and the curvature is clear.