Serial number breakdown shows that watch was either made in October 1981 or October 1991. So if you're thinking it's 90s then October '91 is probably most likely.
That said, I think it's probably a goner. There's rust staining around the date window which is never a good sign to see inside a watch. Given the state of things it looks like it took a big drop at some point. It would require work to reattach the logos and date window frame if you even wanted to attempt saving the original dial, the hands may or may not need replacing depending on whether they're bent or corroded, the crystal should probably be replaced as well (which is luckily easy to source), and of course the full suite of gaskets should be replaced as well. If the movement is rusted you'd basically have to go straight to a movement exchange, I really don't think it's worth trying to restore a rusted up 7009. Unfortunately I'm also unsure whether there is a readily available new movement which is an interchange for it either. There are lots of Seiko modding communities that may have that information though.
My honest opinion is that it's not worth trying to save if it does have moisture damage. If it doesn't then it's iffy. If he watch has good sentimental of family heirloom value that obviously changes things though.