At the moment (2021) not much is known about the exact instruments that Hand Reichel built, with the exception of the Daxophone, which is a well documented instrument with many copies being made by various makers around the world. Reichel made many experimental guitars which are poorly documented.

The Daxophone is by far the most famous instrument built by Hans Reichel. The instrument has become a sort of icon for the experimental musical instrument world and is one of the few to be openly adopted and played by many experimental musicians.

Here is the Daxophone Information PDF taken from the now defunct Daxophone website. This document details the construction process for a Daxophone. I have taken the liberty of hosting it here since the original website is down. ¹⁾

There is some recordings of this instrument as well as this short video shown below.

A short narrative about Hans Reichel by Daniel Fishkinand that details making a Daxophone in his studio ^{2) 3)}
Again a link to the original PDF on how to build a Daxophone ⁴⁾
The original website daxo.de is not readily available because it was running adobe flash, if you have the ability to view the website using a lineage viewer, the original website is still viewable ⁵⁾
Here is a youtube video detailing the website as intended ⁶⁾

I find the video of Reichel's Pick-Behind-the-Bridge-Guitar really fascinating because the video is from 1986 which seems early for experimental guitars like this. This is a point that needs more research as I also think Bart Hopkin and Yuri Landman drew inspiration from these experimental guitars.