On June 21, 1943, the US Supreme Court upheld Tesla's radio patent number 645,576.
Judges of the United States Supreme Court revoked Marconi's patent because they found that it was preceded by Tesla's practical achievements in radio broadcasting

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And to one who is not an expert, it is clear that the patent on the right is a replica of the one on the left
It is unclear what it took the court more than 25 years to consider

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Tesla sued the Marconi Company for infringement in 1915, but was in no financial condition to litigate a case against a major corporation.
It wasn't until 1943—a few months after Tesla's death— that the U.S. Supreme Court upheld Tesla's radio patent number 645,576. The Court had a selfish reason for doing so. The Marconi Company was suing the United States Government for use of its patents in World War I. The Court simply avoided the action by restoring the priority of Tesla's patent over Marconi.

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Markoni received the Nobel Prize 25 years earlier, and Tesla died a few months before the verdict.