Can Someone Identify These Objects?

Mysterious balls found near Compton Verney. What are they?
Image courtesy of James Tuffen

Hi there.

About 30 years ago I was walking in the woods near Compton Verney house when I stumbled across a stash of these items. I was wondering if someone might identify what these could be?? I have my thoughts on what they are but I’d like clarification if possible. I have around 10 possibly a few more but all the same size.

Many thanks, James