A Casascius coin is a physical form of cryptocurrency that was created by Mike Caldwell in 2011. It is a type of physical Bitcoin, which means it represents a specific amount of Bitcoin stored digitally. The name "Casascius" is a combination of the words "casa" (meaning house in Spanish) and "cious" (from the word "precious"), reflecting the notion of the coin being a precious store of digital value.

Casascius coins are unique in that they have a hologram sticker on the back, which conceals a private key. The private key is necessary to access the corresponding digital Bitcoin stored on the blockchain. This feature allows the physical coin to securely hold the value of the digital currency it represents.

The physical aspect of Casascius coins makes them popular among collectors and enthusiasts, as they combine the tangibility of a traditional coin with the value and potential of cryptocurrency. However, it's important to note that Casascius coins are no longer actively produced due to regulatory concerns. Nevertheless, existing Casascius coins continue to be traded and sought after in the cryptocurrency community.

A Casascius coin is a physical representation of Bitcoin, created by Mike Caldwell in 2011. These coins contain a private key hidden under a tamper-evident hologram, which allows access to a corresponding amount of Bitcoin on the blockchain. The coin’s value is tied to the Bitcoin stored within it.

Casascius coins come in various denominations, such as 1, 5, or 25 Bitcoins, and are typically made of brass, silver, or gold-plated materials. The hologram on the coin prevents unauthorized access to the private key, making it both a collectible and a secure method of holding Bitcoin.

However, production ceased in 2013 due to regulatory concerns, making Casascius coins rare and valuable among cryptocurrency collectors today.