Not sure if this is allowed, but I have come across 5 Promethean boards – AP6-75-4k. They were left in a warehouse that I was emptying. Not sure if there is any resale values, if they work or anything? Is there a market for used boards?
These are quite relatively modern ActivPanels, approx 3yr old.
They’ll certainly be a market for resale of these items.
I hope this helps.