If it is genuine, probably a pocket-piece brought back by a returning soldier after WWI or WWII. Yes, old coins (even ancient ones) were souvenir pieces, even back then.
I knew a guy who was visiting the holy land (or Egypt or something like that) back in the 1960s. And as he walked through the crowded street filled with street vendors, he came across one fellow's table , which had a tray set out with handfuls of ancient coins (probably all common). He was hawking them to tourists as souvenirs (and yes, they were real). The street vendor was selling them for something like $1 each. So the guy chooses a couple, and brought them back to the USA with him.
And yes, such souvenirs get lost, just like any other coin. The reason this is so apparent is that you'll notice that around any USA army base, that saw action at WWI and/or WWII, you tend to find foreign coins of those nations : British, German, French, Italian, etc.... That date to what would have been circulating during the war years. Thus : Pocket piece souvenirs brought back by returning soldiers.