This sign was spotted in front of a Japanese game shop and states that the store will no longer be buying back used Xbox 360s that went on sale before August 2007.
The poster tells customers how they can check the serial number on their machine's date. The store will buy Xbox 360s will the dates 2007-09-01 and onward. It's not yet confirmed how widespread this is or if this is merely an isolated incident.
The Xbox 360 went on sale in Japan on December 10, 2005.