21 Inc, the best-funded company in bitcoin, has filed a patent application with the US Patent and Trademark Office (USPTO) for a form of digital currency mining circuitry.

The USPTO – the agency charged with issuing patents to investors and businesses and registering product and intellectual property trademarks – published the submission on 15th October.

Filed in April last year, the filing lists Matthew Pauker; co-founder and chairman at 21 Inc, Nigel Drego; co-founder and chief architect, Veerbhan Kheterpal; president and co-founder and Daniel Fir; co-founder as inventors of a digital currency mining circuitry.

The filing reads

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Although published by the USPTO, 21 Inc's application is still pending approval, a process which can take years. The USPTO process also enables the public to oppose patents if they consider the application in question is unjustified.

The startup, which has accumulated $116m in funding to date, launched its first consumer product – a bitcoin computer for developers – to mixed reviews last month.

The publication of 21 Inc's filing comes after the news that Coinbase had submitted patent applications for nine different bitcoin products.

CoinDesk reached out to 21 Inc for comment, but no reply was received by press time.

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