The big reveal came when they flipped the papers over. Coin 1 was actually the fair coin and Coin 2 was actually the unfair coin. With Coin 1 they had made a Type I error and with Coin 2 they had made a Type 2 error.
We'll see if this helps student understanding when they have their test next Friday - the day before Spring Break! (NOTE: I created this simulation in Fathom and kept re-randomizing until I made errors for both the fair and the unfair coin. If you would like a copy of this Fathom file, let me know in the comments below or send me an email to firstname.lastname@example.org.)