Must have been a hole in the apocryphal Barn roof!Dry stored
One man's rust is another man's dust, and maybe patina!Tbf it does look it's been in the dry for a very long time. Most of that grime is dust. It looks like it's only paint that's flaked and some surface rust formed. Store something long enough in even a dry shed, and it'll get a bit of rust just from moisture in the air unless you spray it down with the likes of WD40.