Huobi has sold all available subscriptions to a new 60-day fixed-term financial product for bitcoin investors.

The latest product from the Beijing-based exchange, which is effectively a bitcoin 'certificate of deposit', is called 'Dig-VC' and offers a guaranteed interest rate for investors. Notably, returns are backed by Digcoin – a new bitcoin mining services platform built by Huobi.

Both will form part of Huobi's Hong Kong-based trading and investment platform BitVC, which launched in June.

Dig-VC subscribers will see a guaranteed return of 1.2% per month (which equates to an annualised rate of 16%), calculated on a daily basis and paid at maturity. Additionally, the first 100 subscribers will be rewarded with an additional 0.2% per month at the end of the 60-day term.

The interest-bearing product differs from 'cloud mining' shares offered by other companies, in that subscribers are not purchasing shares of the hashing power with return rates that vary according to the growth of the network. Instead, Dig-VC promises a simpler investment with a fixed return rate.

Huobi describes Dig-VC as "an attractive new high-yield, low-risk financial product" and offered 2,000 subscriptions for 1 BTC each, beginning this morning China time.

A company representative told CoinDesk all the shares were sold within the first hour, with more than half sold in the first two minutes. There was also a large amount of international interest:

Users may buy or sell shares even during the 60-day term period, or join a queue to do so if no buy or sell offers are available. Sellers who cannot find interested buyers must hold their shares to maturity.

Digcoin is raising investment to significantly increase its overall hashing power. It currently stands at 1.3 PH/s (petahashes per second), or 2.5% of the bitcoin network's global hash rate. It is seeking to raise that power to 4 PH/s.

It will likely begin to offer more 'traditional' cloud mining shares in the near future.

Digcoin has arrangements with Chinese mining equipment manufacturers Avalon and AsicMiner, among others. It is part of the Discus Fish mining pool and sends funds to a publicly released address. At current strength it mines about 28 BTC per day.

While Huobi could not confirm the exact location of the Digcoin mining facility, photos posted on its own information page look very similar to those from a recent report on this large-scale bitcoin mining facility in rural China.

Like other Asian bitcoin exchanges, Huobi has been reaching out to professional investors and traders with a series of products more familiar to the traditional financial world.

It launched BitVC in August, offering derivatives and margin trading to all customers, coupled with 'Yubibao' wallets for eager depositors to make their funds available as leverage to the professional traders. Yubibao accounts (available in both bitcoin and litecoin) earn their holders with a small rate of interest (around 0.017%) paid on a daily basis.

Huobi reports that BitVC has seen new user growth of around 20% per month since launch, and it now accounts for 18% of all Huobi bitcoin trading and 28% of litecoin trading.

Huobi also acquired the multi-signature bitcoin wallet service QuickWallet in August. Customers with accounts at any of Huobi's stable of services may move funds between them instantly, and without incurring fees.

Together with competitors OKCoin and BTC China, Huobi recently completed an audit of its bitcoin reserves that showed it held more than 103% of the bitcoins its records showed.