Vintage silk blouse with mother of pearl buttons

It's a vintage silk blouse with mother of pearl buttons. It's my mom's from before I was born so probably like the 80s or 90s. It's been in a closet for like forever. There's something on the arm, I don't know what it is but I know that you can mess up silk really easily so I don't want to make it worse by trying to fix it. It might come out with a wash, it might not. IDK that's why I'm pricing it so cheaply. Basically this shirt is a gamble. Buy it for cheap and you might have an easily removable smudge, or it might be a stain. I might have it dry-cleaned to see if I can get the mysterious smudge off but then if it does come off it'll hike the price.