Agree with Elizabeth. You changed your mind after entering into a purchase agreement. If I were the seller I would be very wary that you were trying to run a scam. (Not that I think you are, but solely from the seller's perspective). You should have accepted the item and then tried to resell it. There's demand for the 707 and it should sell quickly.
In your defense of your pre-purchase research, the B&K 707 is a tricky item.
In your defense of your pre-purchase research, the B&K 707 is a tricky item.