u/BSBlazing450

Hey there! At my semi-recently deceased Grandmother’s place cleaning the house and all with other family members when I went into her bedroom and saw this. I’m not too familiar with mold or how it looks as I’ve only ever dealt with it once in my life before but was wondering if this was mold or some kind of dirt. This is a window unit that’s right up against the bed of where my Grandma used to sleep, and the window unit still works too! If it’s mold should I just throw it out all together??