You can risk it, because in 99% no one will have a chance to prove to be the copyright holder. Thats the way that
imho the most commercial publishers go with german ww2 photos. And after publishing they try to hold the "copyrights" that they never had.
Thats my personal opinion.
Btw, in germany the lawfully copyright holder (in german "Urheber) have to prove that he have the copyright. If he cant to that the law will not give him the rights. Who can clearly prove after 50 years and more that he was taking this one picture?
Its to complicated for me to explain it with my poor school english. I hope you understand it?