In one of my tractors (in Norway) I found it filled with some sort of rusty sand. And it was most in the rear end of the engine. I don't know if you are familiar with the Ferguson TEA 20 with the Standard engine.
Here you can see a picture of it,
http://www.fergusonplus.com/ The tractor in red primer. Here I have cleaned it all out, and the sleeves are out, or liners as the British call it.
In the rear end it was like 80% filled with this sand, and then it sloped down towards the first cylinder where it was maybe 20% filled.
I have never to this day neither before nor after seen that kind of rusty sand in an engine. And I can not imagine someone filled sand in it, and I am 100% sure there was no sand in it when it was assembled at the factory. I have many times wondered where the sand came from.
Bill