The U.S. Government’s Secret Inventions (top of the iceberg info)

a simple search resulted in:

The U.S. Government’s Secret Inventions

Secrecy orders allow U.S. defense agencies to control patents, including those that are privately developed.

https://slate.com/technology/2018/05/the-thousands-of-secret-patents-that-the-u-s-government-refuses-to-make-public.html