mystery instrument number 1 solved... by me!
I got a small Tobacco tin from a charity shop and decided to make it awesome. I cut some small mounts and drilled some tiny holes so that it could be 'suspended' in the middle of the wooden frame, that way the sound wouldn't be dampened so much. I put a piezo transducer inside the tin because I was afraid it would be far too quiet, but it actually managed to amplify the sound pretty well without it!
Definitely something I can make many more of, so if you want one, let me know and I'll make you one!