In 1967, Swiss motorcycle racer Fritz Walter Egli founded a motorcycle workshop where he reworked a Vincent Black Shadow and fitted it with a central tube frame. Egli won numerous hill climbs with this machine and became Swiss champion in 1968. He ended his racing career and specialized in developing exclusive motorcycles with powerful engines in optimally tuned chassis. To this end, he purchased several Vincent engines, which he further increased in performance and then mounted in his own advanced custom-built frames.

The Egli-Vincent is one of the most famous motorcycles built by Fritz Egli. Between 1967 and 1972, around 100 were manufactured. Various media outlets often refer to them as "the best café racers of that era." High-quality replicas of the Egli-Vincent were manufactured in France by Patrick Godet, who passed away in 2018.
The text is taken from https://de.wikipedia.org/wiki/Vincent_(Motorradmarke), and the photos are mine.
This beautiful motorcycle and many others are on display at the PS.Speicher vintage car and experience museum in Einbeck.