High Mileage badges are awarded at 250,000km, 500,000km and 1,000,000km
AKA, 155,342mi, 310,685mi and 621,371mi.
Just go to an MB dealer where you fill out a form, they verify the odometer reading, and then send it into MB headquarters. You get a certificate for hanging on your wall, and a badge to put on your grille (all for free). I've got the 250,000km badge and wear it proudly.
peace,
sam