What can I do with an old Harbeth M30 midrange driver

I have an old Harbeth M30 driver sitting around the house. It came from my old M30. I thought there was something wrong with it so I replaced the driver. Upon further inspection, I can't seem to find any perforation with the driver and the driver looked okay.

So, I now have this extra driver. What cool things can I use it for? Can it be resold for someone to figure out if there is anything actually wrong with it (if any)? I need ideas.
Why would you have replaced it thinking something was wrong with it and now, after running across it, figure nothing is wrong with it? Throw it away and move on.
If we can put together a couple of free midranges, bass drivers and tweeters I'll take them and build my own speakers!

I'll even create a thread to document my progress or utter lack thereof.