Since digital card holder Coin was announced last November, the team behind it has done a lot of thinking. To battle fraud, they've implemented an optional morse code unlocking system. To help manufacture the more than 20,000 Coins pre-ordered, the company poached Apple's iPhone supply chain guy. To improve Coin's two-year battery life, the device's magnetic strip now only turns on at the millisecond it's being swiped. Coin even hired two outside security firms to audit their entire operation from the inside out, and built a system that could allow each Coin to send a unique code string to verify every transaction, which would "obliterate" fraud, says founder Kanishk Parashar.

But Coin is far from finished. The device was set to ship this summer, but as of today, Coin only works at 85 percent of credit card terminals. The remaining 15 percent correspond to edge cases, since every credit card terminal is different, says Parashar. Just this month, for example, the company made some fixes to make Coin more reliable at ATM machines that eat your card. The goal is to reach 100 percent, of course, so today the company is emailing its backers to ask if they'll help test Coin over the next few months, and report back on how it's working. 10,000 backers will be accepted into the program.

As of today, Coin only works at 85 percent of credit card terminals

The opt-in "Coin Beta" program has an interesting wrinkle, however. To get a Coin prototype months early, you'll have to sacrifice the final retail Coin you ordered. But, if you want to replace your beta Coin with the real deal when it ships this spring, the company will sell you one at 70 percent off. Plus, Coin Beta testers will get 50 percent off any Coin products they buy over next three years, which could include additional Coins or other accessories.

Coin's new beta testers will complement the street teams already deployed in San Francisco, Los Angeles, and New York City, who have been going from store to store testing Coin. "We've already checked out every nook and cranny of San Francisco, so our nationwide beta will be a good way to figure out where something is incompatible," says Parashar. "Nobody has made something like this before, so we can’t read about the lessons others have learned." Already, however, Coin seems to work pretty well. Parashar says that not a single beta tester thus far has had their Coin rejected by a cashier or waiter. Then, he spent half an hour demoing the entire Coin onboarding process for me. Afterwards, he took me to a bodega to prove that Coin works in the real world. Then, I tried Coin myself at an ATM.

Parashar says that not a single beta tester has had their Coin rejected by a cashier or waiter

In short, Coin works. It all starts with the Coin app, which launches on August 28th for iOS and September 25th for Android. Using a Square-like card reader that ships with Coin, you can swipe your cards one by one into the app. Then, you can flick through them all in a neat Rolodex-like interface, and choose which eight cards you want to transfer to your Coin. When you're ready, you can press down for a few seconds on Coin's button to start syncing cards over Bluetooth. The process is incredibly simple, and provides some early hints at what Coin might do beyond selling digital cards. Coin might be the most successful of any company yet at truly replacing your wallet.

"It’s more a digital commerce system than a card system," Parashar admits. "What we're really building here is a set of consumers who trust our system and are able to utilize our system to do transactions. That enables us to use any technology to do the actual transmission." And, you can add any number of cards to the Coin app — even membership cards and insurance cards that don't have magnetic strips. You can imagine a future where the Coin app, or even Coin itself lets you keep track of all your "cards" and even pay over NFC or Bluetooth. "I saw a tweet this morning from [venture capitalist] Marc Andreesen saying 'Most ideas are great — the question is if the timing's right. When you have the timing right, you almost always feel like you're too late.'" says Parashar. "And right now, I'm feeling a little late."