This, apparently. Not only have we never seen 500 Servebot Dead Rising mugs, we've also never seen Mega-Man creator Keiji Inafune sign 500 Servebot Dead Rising mugs. Now we have.
Beware: This clip has clinking noises. If you are sensitive to clinking noise, might want to turn the volume off.
Keiji Inafune Signing 500 Servbot Mugs by Hand [Capcom Unity]