There are archives in every place. As big as the country, as small as the province, as small as the county seat, there are, this is a government agency, files are not allowed to be destroyed, (except in special circumstances. So most people's files are kept in the archives.
Moreover, files can be opened, but many people don't know it.
You can go to the archives and ask yourself. Of course, the museum will ask you to show some documents, immediate family members and so on.
China is a super powerful country, and everything is under control, which is beyond your imagination. In your grandfather's time, files were extremely important, so there would be many unexpected things in them.