A UPC bar code is for the product type, not specific to that product. However, some stores now use RF tags that are specific to that item. You will also be asked for a receipt which you do not have. I suppose you could say it was a gift. If this item is over $100 or so, be prepared to end up in...
Only parakeets buy things on Craig's List. CHEAP CHEAP CHEAP. Get it? I know, it was a horrible joke. But the point is valid. People go on CL looking for a really good deal. You can try listing it at $700 and see what happens. But you will probably get a lot of low ball offers, for $500 or less...