Belgian 5 Francs 1873 -Any Idea What This Countermark May Signify?

Whenever I see a name and a long string of digits stamped onto something metal, I always assume it's some kind of military ID tag. My guess? Perhaps a serviceman's replacement "dog tag", made from a locally-found silver coin while they were in the European theatre. Given the age of the coin, my guess would be World War I, rather than World War II.

The name appears to be English in origin, so I'm assuming the serviceman in question is either British or American; it's not British-colonial (eg Australia or Canada), as colonial soldiers usually have a letter-prefix to their service number indicating the colony they came from. I assume you've found it in America, so I'd start with there.

The "dog tag" theory also explains the two holes drilled into it.