Why would a person create a fake birth certificate with a clod of whatever stuck to it....?
If you’ve ever kept old documents, as I have
boxes of them ;), many of mine have similar
deterioration or brownish/rust stains, etc.
on them, especially when the old staples,
paper clips were used, which weren’t made of
the more rust free used now.
Plus any drops of anything on the paper could
oxidize over the years and show up, and
non-acidic paper definitely ages noticeably.