In 1995, I was walking the battlefield of Verdun, when my ex-wife (my girlfriend at the time) saw a rusted fragment of metal in the mud. She picked it up, and after bringing it home and cleaning it off, it turned out to be a French identity disc, with a French name and "158" barely visible.
Two decades later, I've made the acquaintance of a French husband of a friend of mine, who has just researched his own uncles' and grandfather's service in the Great War. I tell him about the identity disk, and he is interested in it. I loan it to him, and after a few weeks research…
He finds the soldier's war records online (about three pages: he was a draftee for the 1913 callup). Apparently the French Ministry of Defense only recently put records of soldiers of the Great War online. He finds the website showing the village memorial to the dead, with the soldier's name on the memorial. He finds the history of the regiment, together with its service at Verdun in 1915, and the records of the soldier's death.
And finally, after a few weekend calls to families with the same name, in the same French village where the soldier was conscripted, he finds the man's last living relative, a great-niece, who remembers stories of her uncle and would be thrilled to have his identity disk. So tomorrow I'm off to the post office to mail her her great-uncle's identity disk.
It is absolutely amazing to me what information is available online and what smart people like this friend of mine can do with a little research…