Gherkin with germanium diodes
There is no benefit to using these over a 1n4148 silicon diode in a normal keyboard. They do look very different. The glass is brittle compared to the glass in a 1n4148 diode.
If building something battery powered, the lower forward voltage would keep the matrix functional at much lower voltage levels. Schottky diodes could also be used.
40% Edward keyboard was also built with these.
Some measurements of different diode types in a keyboard matrix