Original House Drawings from 1924 Show Possible Issues

I dug into the original house drawings from 1924 and found many interesting things that may relate to issues I've had like sporadic sewer odors, unexplained wall cutout, etc.

There are a number of waste lines all running into a main trunk. From refrigerator waste, plumbing, laundry trays, a floor drain (if that was covered over or abandoned that could be a source of sewer odor if it was ever connected to the sewer.) I don't know what the D in a circle symbol is. House didn't connect to sewers until 1955, thirty years after these drawings.

These drawings do not always reflect the way the actual house was set up. e.g. house never had a furnace, always a boiler. In this case waste lines are showing at the basement front, whereas in reality they —and the laundry—have always been in the back of the basement —notice my blue 'septic tank' conduit note where there was a cutout in the rear wall of the boiler room. Yet strangely, exactly where that front drain line ends at the front basement ball is where I found a 7x7 cut out to the outside where it says 'cleanout pit'. This is nowhere near the fireplace, so perhaps years ago on the outside there was some kind of accessible pickup pit. Also some symbols some of you might better interpret.