So of course I needed to destroy the devices well. Despite the drives over the past years being formatted, blasted with random data, files being overwritten, encrypted and decrypted something stronger and more amusing was needed.
At the time I was burning some documents and shredded paper so I thought I would throw in both USB's to see what happened. After waiting a few hours for everything to cool down I found one USB and surprisingly it was mostly in tact.
After cleaning, washing, filing and drying - amazingly the computer detected it but the below appeared.
These things are seriously tough! In the end to finish it off I snap it into a few pieces and even that was hard since its small and rigid.