The invention means little to people today, but the testimony shows how much significance the Founding Fathers of the US attached to patents in terms of national security and growth: It bears the written signatures of George Washington, his secretary of state Timothy Pickering and attorney general Charles Lee.

In its early years, the new republic held invention and the establishment of a patent system dear. The first patent act was enacted on April 10, 1790, and, three months later, the first patent was granted to an inventor for his improvement in potash production.

An explosion of patent applications followed－by 1836 more than 10,000 patents had been issued, and all were signed by US presidents－before major changes were made to make the system fairer.

Even Abraham Lincoln himself obtained one in 1849 for inventing an instrument to lift boats over shoals and obstructions in a river, making him the only US president ever to have registered a patent.

Lincoln said the US patent system "adds the fuel of interest to the fire of genius in the discovery and production of new and useful things".

The application process was also opened to foreigners. Featured inventions at the National Museum exhibition demonstrate the creativity of people hailing from around 16 different countries who lived in the US at the time.

David Cole, executive director of the Hagley Museum and Library, says these models are not only figurative representations of practical thoughts but also great pieces of art, because inventors largely worked with craftsmen to make the models, with a keen eye on aesthetics in a bid to further impress examination officials.

As patent applications boomed, keeping the models put the patent office under huge pressure and, after 1880, models were made only when asked for by examination officials.