It all started from an old piece of dry slime that no one believed was still viable. Read my post here: https://www.facebook.com/share/p/18bH2PfGyc/
All I know is it is from the Southern US. I activated the dry slime and for 10 days it showed no sign of life, until I found a tiny string of straggler on the underside of the paper far away from the sclerotium. I moved it to an agar culture and it came back to life, and has since become my favourite slime child.