Personally, I would be interested to see how many "old" PM'S that have been shipped over to impoverished countries are in use.
Years back, I worked in a school during the switch from Acorn machines to Windows based machines. We boxed up all the Acorn stuff and donated it to a charity collecting working computers for poor countries who wanted to provide at least some basic IT education.
Granted, the comparison between Acorn and Windows is beyond the point now, but I do know quite a few schools donated old machines and equipment to similar charities during the first few years of the new century. I wonder who uses them now, if at all.