I have always thought that SOS was creamed chipped beef (on toast). ?? Stouffers makes a nice little frozen version.
Another good variation is Williams white gravy with sausage bits. Comes in packets, dry. You just add 2 cups water and heat, and it is AMAZINGLY good for how easy it is, for those who like biscuits and gravy.
My mom made that, and every time she made it, we added a new drinking glass to the collection.