Nikola Tesla was an inventor who obtained around 300 patents[1] worldwide for his inventions.
[2] Many inventions developed by Tesla were not put into patent protection.
In various patent logs, it is recorded Tesla applied for US patent #613819 for "Filings Tube" (such as Charles Henry Sewall's "Wireless Telegraphy" (New York, 1904)) but it does not seem to have been issued.
The total number may be incomplete and additional countries still may hold patents unknown.
Devices and projects Tesla proposed and partially designed but did not patent.