Name: Ravenbit NODE coin (standard edition, brass)

What it is: A physical 'bitcoin' token that can be loaded with value or kept as a collectors' item.

Made by: Ravenbit.

Cost: $20 plus shipping (less if bought in bulk quantities, more if limited edition).

Basic summary: The Ravenbit NODE is a physical bitcoin token with no pre-loaded value (to comply with money transmission regulations), to give as gifts or keep as a collectors' item. Users install bitcoin value by attaching printed QR codes, and as such the coins are re-usable.

CoinDesk rating: 3.5/5

Composition: 85% copper

Color: Gold

Diameter: 39mm

Thickness: ~2.5mm

Weight: 0.95oz

Inside the package from Ravenbit is the coin itself, in an airtight round plastic coin case and a felt pouch with the Ravenbit logo, two hologram stickers to seal the QR codes in, a Ravenbit sticker and a clear acrylic display stand.

The obverse side of the coin features a 'nodes' motif consisting of one large bitcoin 'B' logo in the center surrounded by 25 smaller interconnecting logos. Some of them are tiny, and the level of detail is such that examining even the smallest ones with a magnifying glass reveals accurate lines.

The reverse is mainly blank with an indented square to hold printed QR codes. Around the rim are the words 'bitcoin', 'Ravenbit', four raven logos and a braid pattern, plus the minting year. The edge of the coin is dead smooth, without reeding or lettering.

Ravenbit's site has instructions on how to add actual bitcoin value to the coin.

Here's where the process gets fiddly. To actually use your Ravenbit coin as a cold wallet you'll have to print both your public and private keys as 0.55-inch (14mm) wide squares onto paper, cut them out and attach them to the coin somehow.

Ravenbit actually has a client-side javascript (i.e. works offline) generator on its site to produce the codes at the exact size required (something I discovered only after about five minutes messing around with photocopier reduction, which was unadvisable and entirely my fault).

At those sizes, the higher-resolution printer the better, but I was able to produce codes that scanned easily even with an average inkjet. Inkjet prints have questionable long-term durability though, so you'll probably want laser printing or a photocopy. Ravenbit recommends you keep backups of the codes/addresses in a safe place, which is good advice for any cold wallet.

Ravenbit's site, unlike some other cold wallet producers, does not offer to generate your keys for you. This is a positive, as you should always generate keys offline. Services like Bitaddress.org and BitcoinPaperWallet.com have downloadable generators to use this way.

For added security I created a BIP38 encrypted wallet with a secure password, meaning that even if someone could scan my private key, they could not easily steal my bitcoins.

To attach these tiny keys to the Ravenbit coin, you have to cut them out and stick them in the indented square on the back of the coin. The instructions say to place the private key face down underneath, and the public key on top facing outward.

Of course if the coin isn't intended as a gift to someone else, you could always leave the private key off altogether and store it in a safer place.

You then cover them with the transparent hologram sticker provided and voila, if you can get it centered properly without messing up, you actually have a pretty nice looking coin. If you're the kind of numismatist who thinks things like QR codes and holographic stickers are appropriate design elements on coins, that is.

One advantage of this method is that the coins can be re-used: once you've removed the sticker and swept the private key, you can simply print new QR codes and stick them on. Ravenbit sells replacement hologram stickers as well.

With the demise of legendary coin producer Casascius after FinCEN defined its business model as 'money transmission', physical wallet manufacturers have had to take a different course.

No longer able to imbue their products with actual bitcoin value before sending to buyers, it is now mostly the buyer's responsibility to set up a wallet and add bitcoins to it.

Several of the physical coins CoinDesk looked at in September are now either out of stock or off the market, suggesting the market may have been limited.

Coins are also not the most practical form factor for containing both a public and private bitcoin key, allowing senders to see/scan one without revealing the other. Ravenbit's compromise uses paper and stickers.

I confess I have a personal fascination for the coin form factor, and there's something inherently satisfying about the size and weight of a one-ounce metal coin in the hand, which the Ravenbit coin fulfills.

Despite the impracticality of using a 1.57-inch diameter metal disc as a bitcoin cold wallet, coins are still great as gifts, conversation starters, and a metaphor for bitcoin as money that even non-users can relate to on a visceral level.

I gave my wife a metal Cryobit cold wallet as a christmas present. While the weight of the stainless steel and resilience of its ceramic glass etching are impressive, it went straight into her wallet and hasn't been seen since.

Had I given her a Ravenbit coin instead, it might have stayed out long enough for people to see and talk about it.

From experience, pulling out the Ravenbit coin to show non-bitcoiners always generated a few ooohs of interest and saw the coin get passed around, with even the odd "Oh, is that an actual bitcoin?" or "I've been thinking about getting into bitcoin" thrown in.

Metal coins work as a skeuomorphic avatar for bitcoin as 'money' and 'value' in the 'real' world, and the word 'bitcoin' itself invites their existence. They are also, it seems, necessary to create clip-art for bitcoin stories in non-bitcoin news publications.

Images via Jon Southurst