I know that for Dreamcast Clare L.E (1800) there is a sticker with a serial number. There were consoles without number?
They did a small second print run, The ones without the serial number stickers also come with the white cover Biohazard CV complete (T-1240M) instead of the original LE with the Red Slipcase.
Kron is absolutely right - the unstickered red Biohazard DCs were a second print run just sold by D-Direct in Japan. They are only 50 unstickered red Biohazard DCs.