Surprise boules

One of our Canadian friends spending the winter in S. Florida brought us some "boules". He had bought them at a flea market. They looked all right on the outside, but they weren't rolling very straight... So he decided to give them a good whack with a big hammer, and look what he found. He brought them to us as a souvenir when he came for - you guessed it right - a new set of real boules.


They're macro pics, so by clicking on them you get a close-up.
I swear we're not making this up!

We wondered why a factory would go through the hassle of forming a glued sort of sandball, sticking a threaded rod through it, and then cast the metal around it.
Well, sand casting is a traditional, though quite labor intensive foundry method. No need for welding.
But the most likely explanation is that sand is a lot cheaper than steel, especially since steel prices have almost tripled over the last 3 years.