I would bet its actually 2 modifications. First was blow out the front of the roof to make the second floor usable floor space larger. Then the did the rear/left addition.
Go drive around cape cod and you will see all sorts of funky additions on 200 year old houses. that might have been 600 sqft when built.
edit this house is on Cape cod and has been in my family for 100 years, my distant cousins still live there. The first section of the house is 200 years old.
What it looks like from the street.
Attached Filethis is the best shot of the side/back I can get. Its 4 additions, one was blow out the second floor rear, next was a rear kitchen, then they added a second floor to the kitchen and finally they added a large addition on the rear
Attached File