My guess is that you will need to wait 70 years for it to enter the public domain or until any heirs are found. If you decide to sell a book with these photos,

My guess is that you will need to wait 70 years for it to enter the public domain or until any heirs are found. If you decide to sell a book with these photos, you risk of some rightful heir coming out of the woodwork and suing you for damages. The case of Vivian Maier comes to mind.