Someone is going around San Francisco and leaving small sheets of aluminium all over the city. No, they are not littering. The sheets are in fact bitcoin 'paper' wallets – part of an elaborate scavenger hunt that is being carried out by an anonymous and fun-loving donor.

The hunt has its own twitter account, @SFHiddenBitcoin, which carries the slogan: 'Bringing bitcoins to the people by hiding them. An educational experiment'.

The account reveals clues as to where the wallets might be found, and acknowledges when they are found, but it is a mystery as to just who might be behind the stunt.

Clue #2: There's no printing press here, but they do accept Bitcoin. pic.twitter.com/19PaldAA2T

— SF Hidden Bitcoin (@sfhiddenbitcoin) July 10, 2014

The wallets are neatly designed, black-on aluminium cards, displaying a bitcoin address, a QR code and the name of the twitter account. Each one is said to contain 0.0333 bitcoin, or about $20, which goes to the lucky finder.

Many of the twitter clues reference pop culture icons, movies and TV shows and are obviously designed to amuse. One is a play on words on the Facebook movie tagline: 'You don't pay $10m for a house without making a few enemies', and it is believed the card is hidden somewhere near Mark Zuckerbeg’s house.

@SFHiddenBitcoin claims the scavenger hunt will go on for a month, with a new wallet stashed away in a new location every day of July. So far all the cards have been found within a short time of the clue being released.

The scheme closely resembles the Hidden Cash scavenger hunt organised by billionaire Jason Buzi in May. Buzi buried money in plastic toys in several locations in California and elsewhere, and the associated twitter feed eventually ended up with 700,000 followers.

@SFHiddenBitcoin currently has 219 followers, but media coverage is picking up, even at mainstream news outlets. Business Insider ran a brief feature on the scavenger hunt yesterday, while SF Weekly covered it today.

Wallet image via @sfhiddenbitcoin