News from French Xbox website logic-sunrise.com tells us the French retailer Micromania is now checking each Xbox360 with a Halo3 "DVD+R DL RW" (whatever that is lol) disc before buying it back from customers and putting it on the 2nd-hand market.
According to their source at Micromania this discs is coming from Microsoft itself (!?). This is a quick test to see if the DVD FW has been flashed with a custom firmware - and would avoid the 2nd-hand buyer to be banned at a later time not knowing his FW was flashed. Of course you can still flash your DVD FW back to stock FW before selling it Wouldn't really detect already-banned consoles either, but I'll assume they do a different check for that.
If other shops out there received a similar disc or got instructions from MS about how to detect flashed DVD FWs and banned consoles for 2nd-hand 360s, feel free to let me know xantium /AT/ xbox-scene /DOT/ com