I used coins to create my alphabet, covering them in tipex and hand writing each letter onto both sides. The choice of tipex was due to a series of tests i did beforehand, showing that things such as paint, vinyl or spray paint reduce the coins spinning time in half, whereas tipex only slowed the coins by 0.04 of a second on average.
I used 1p coins for small letters, 2p coins for caps and 5p coins for punctuation and numbers.
We also had to create a sound for the animation, for which i recorded the coins sliding down a piece of cardboard. I sped the recording up by 2000x and reversed it to give the odd fluttery effect.