A more detailed example: I was scanning some family photos (for backup/archive/family use, no publishing as of now) and noticed that several have small stickers marked with copyright notices of the small town photography company that took them. I asked my family members and they said the company is no longer in business, but I worry that those photos will never be able to be published until after well over 100 years after it was taken. How can I track down the copyright for such photos?