Every bn will have a challenge coin (or several, sometimes the senior NCO will have his own design), so there's a unique design for roughly every 1,000 people in the army, and they get redesigned fairly often, because the command teams change out after just a few years and often want to have their own version.

Which is just to say that it's fairly common for someone to go googling to look for images to put on challenge coins, not that it's normal for yours, out of billions of possibilities on the internet, to have been picked out :)

Please tell me they did you the courtesy of sending you one of those coins...