What is autopen signature? Ex-US President Joe Biden accused of using device on key White House orders

Previous United States President Joe Biden, who vacated the office in January, has been accused of using an autopen signature on many crucial documents during his time in office.
The Oversight Project, an initiative of the conservative Heritage Foundation, made the sensational claim in a report released last week, raising serious concerns about the authenticity of Biden's executive orders and his cognitive abilities.
But what exactly is an autopen signature?

Autopen signature's use
An autopen signature is one that is produced using an autopen, also known as a signing machine. Autopen is a device used to mechanically make the same signature, and its use is common among people who may need to sign quite frequently. It is often used by celebrities and government officials. The device allows signatures to be made without the physical involvement of the signee.

History of autopen
The first signature-replicating machines were developed by English inventor John Isaac Hawkins, who received a US patent for the device in 1803. The autopen became commercially available in the 1930s. It is said that the first commercially successful autopen was developed by Robert M De Shazo Jr., in 1942. Following the development, Shazo Jr. had reportedly received an order for the machine from the US Secretary of the Navy.

Use among US Presidents
It is believed that Thomas Jefferson -- an American Founding Father and the third president of the US -- extensively used the automatic signing machine during his presidency in early 19th century.
In contemporary times, former US President Barack Obama and the current president Donald Trump have also famously used the autopen to sign official government orders.

However, signatures made using an autopen are generally valued less and perceived to be somewhat inauthentic. They are also susceptible to misuse since the signee's direct involvement is not required.