Dish Network Satellite Receivers and R00 Numbers
Buying guides will often tell you to ask for the r00 receiver and call Disk Network to see if there is a balance.
While this might be a nice thing to do if the seller is unsure of the history of the receiver, it does not protect you from fraud.
Just because a seller lists a number and maybe even has photos of it, that does not prevent the seller from giving you a fake number from another listing, from a retailer or dealer display, a serial generator, or even the trash. People that are successful at commiting fraud have a good learning curve and are often ingenious.
Do not be lulled into a false sense of security because the seller lists the equipment number.
The best way to protect yourself against a seller you don't trust (yet) is to purchase with a credit card (you can purchase with a credit card through Paypal) or use escrow.