Washington (CNN) There's a challenge of a grand jury subpoena that's now before the Supreme Court -- and very little is known about it. Still, the case has gained widespread attention after it was connected to the special counsel's investigation into Russian interference in the 2016 presidential election.

While the Mueller-connected case progressed through the courts, secrecy around it grew.

At first, Mueller's attorneys showed up to hearings last fall that took place unannounced inside a locked courtroom. Once the judge held the company in contempt for noncompliance, the back-and-forth over an appeal stayed largely anonymous. When the attorneys argued the case at the DC Circuit Court of Appeals, an entire floor of the courthouse was locked down by security, and the attorneys came and went without being seen. The Supreme Court has now allowed the company to file its argument under seal, with any identifying information redacted from the public's view.

The company and the country remain anonymous.

Yet the growing collection of court filings reveals bits about the country involved and the company from which Mueller wants information:

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