I have had a situation where a DFC purchased from a reputable network equipment broker turned out to be a 3B even though it was marked as a 3BXL, and the broker had run the serial number and it came back as a 3BXL. However the broker resolved the situation. It appeared likely to the broker that the DFC was from a grey-run (via a third party he previously trusted as a new box pull source). This was the only DFC I'd purchased through a broker, and didn't exactly encourage me to purchase any further 6500 components through a broker.