I once read some account or theory of akkadian proto-currency. Market officials would issue clay coins stamped with a pictogram in exchange for goods like cattle or wine. These coins could be exchanged in the market and then would be be cashed in for the goods at the exchange. At that point the coin would be smashed. I guess more durable goods like wine could be stored long term in the exchange and the coins could function as a medium of exchange.

You could do something similar with bitcoins that might be fun on a campus. A trusted bank-like-thing issues clay coins that can be smashed to retrieve the private keys. It might be nice to be able to go from digital back to clay from time to time. It would be interesting to see if they trade at current bitcoin prices, how many get smashed, etc. It also adds a layer of anonymity that can be seen and understood by non tech savvy folks.