James H Schmitz's "Legacy" aka "A Tale of Two Clocks" (novel, space opera, free): Many groups are after the ancient treasures
Story summary.A star-traveling humanity has discovered a treasure left on some world by long gone "Old Galactics". Treasure comprises of a number of "plasmoids" - a kind of artificial-life agricultural robots. They can produce so much food, we'll never have to worry about it, etc. But the process of human acquisition of them had shut them off, & no one knows how to turn them on again.
Currently they're in custody of the government, but sundry other groups want them too. And what will happen when varied groups begin doing their own underground tinkering to revive these ancient living machines...
- James H Schmitz's "Harvest Time" (download): The story where "plasmoids" were first discovered.
Fact sheet.First published: 1962.
Download full text from Baen Books, Project Gutenberg, Manybooks.
Download audiobook from Internet Archive, LibriVox.
Related: Stories of James H Schmitz.