GeorgeB 
I have run a lot of cell phone boards, if done right, as a refiner, they can be very good to process. There are a lot of other metals besides the gold. To get an average on how many are in a lb however is impossible to be honest. If you are only talking about the boards themselves, you have to consider the year they were made, and the country they were made in. For example, right around 2002 the Nokia 3310 was a very popular phone in third world countries as well as in the United States. In third world countries, like South America, most of the phones were actually knock offs that came from China, and although they were able to perfect copying, they didn't use nearly as much precious metals and the boards are actually much lighter than the real Nokia phones that were being made in Finland at the time.
Other things to consider is the frequency the phones operated at, the technology used in the radio, if they have more buttons like a smart phone has gold under each button on the phone, etc. It stands to reason the more buttons, the more gold, the heavier each board will be, the fewer boards in a lb. Another thing to consider is the year they were manufactured, if before 2002 the technology to plate gold wasn't nearly as advanced as it is today for example, but when gold prices jumped in 2002, industry responded immediately by using methods that deposited far less gold, and in the years since the plating technology has become better and better, so newer phones have far less gold, and thus you should have more per lb than others, unless it's a smart phone in which case the gold under the buttons increases the weight significantly. And on and on.
Even figuring out how much gold you can extract per lb is almost impossible. You really have to know the material well, to understand which types are the better phones to purchase. And the only way to really know that is to talk with a refiner who does a lot of cell phone boards. But even still, I couldn't give you any accurate count, nor yield, I can eyeball something and approximate fairly well, but that's just an educated guess.
A ton of used mobile phones, (for example - approximately 6,000 handsets, contains about 3.5 kilograms of silver, 340 grams of gold, 140 grams of palladium, and 130 kg of copper. But that still doesn't really answer your question, those figures are for the complete phone, not just the boards. And those numbers are approximate and can vary greatly. You can figure approximate value per lb from this point. I don't really think knowing how many cell phones in a lb matters, when I was buying them I was paying per lb, not per board.
Scott
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