the object in the Drain appears to be an expandable drain plug David…I could only guess to keep out sewer gas but more likely to stop back up …not a good sign i think…I can’t tell about the covered area…anything in sellers disclosure???
The covered hole in the floor is where the original coal furnace used to be; a newer or first concrete floor was poured around it. It has since been replaced with a gas furnace (in back ground) the hole in floor was never properly cemented shut, just covered up! The “Plumbers Plug” is used to pressure test new drain systems and also used to prevent frequent sewer back-up’s, while eliminating your basement drainage system in case of a plumbing bust!