A little bit of useless information

Which may be a little relevant to parents of boys, which in hindsight will probably be blindingly obvious once it's pointed out.

If your boys play with marbles, it generally isn't a good idea to mix glass marbles with steel ones.
The marbles in the old days may have been of better quality and more resistant to this, but the modern ones are mostly cheap factory products.
The impacts with steel ones break sharp slivers and splinters off, potentially dangerous.