Some advice on buying fingers.
1) Pay attention to the cleanliness of the finger boards. Are they trimmed closely to the gold plating? Do the fingers appear to have other debris mixed in, a common scam is to mix in or "salting" of the batch (especially larger batches) with useless junk such as screws, wire, odd pieces of junk, etc.
2) Keep an eye out for mixed batches which contain various grades of finger boards. Older thick plated fingers tend to have wider traces and wider spaced traces. Modern fingers have red, green, purple, etc colored solder masks. The newer ones can be much lower value than the older ones. The much older ones are higher value and the board material is more brown than tan/yellow.
3) Be aware that unscrupulous sellers with access to Cyanide will pre-strip the fingers leaving a very thin Au layer over a shiny nickle layer. These are nearly worthless.
4) Watch for EDIN (*ENIG)(flash plated) Telcom board trimmings and pieces mixed in. These boards look pretty but produce no where near the Au.
5) Watch for batches with board pieces thrown in that only contain a thin ring around holes and edges or large EDIN (*ENIG) plated areas.
6) Do the finger boards have other components or metal near the board side of the finger where the trim cut took place?
I always ask losts of questions about the history of the source of the fingers from the buyer. Also ask for lots of pictures of the material spread out and not just the top of a pile which could be hiding any of the above mentioned pitfalls.
Typically if the price on a batch seems too good to be true, there is a reason for it. If you find 100#s (or even 1000s) of fingers for $25-30/pound and the buyer is anxious to sell, ask lots of questions. Good quality, well trimmed, clean fingers "should' produce 1.5 to 2 grams of Au per pound and will be easy to sell for $50-60/pound at today's spot leaving you a small profit margin when run using the proper methods.
The largest single batch of fingers I've personally ever run was 550# and was a mix of various types across the spectrum mentioned above. Final yield for the batch was 1.25 grams per pound. The entire 550 pounds was run in 8 hrs soup to nuts thru cyanide using a cement mixer doing 30-35# batch sizes in each load.
On the other end of the scale the highest yield fingers I've ever run was nearly 6g per pound final yield. They were pre-1970s 100% clean, all identical, well trimmed, wide spaced thick fingers on dark brown boards.
Steve