Zurich based company Bio Strath was already sponsoring the Swiss Formula 1 driver Jo Siffert, when Clay Regazzoni joined Siffert begin of 1971. Infortunately, Jo Siffert passed over at the end of the 1971 season and for Bio Strath this tragedy was the signal to stop too.
Let see this exclusive documents showing a Clay Regazzoni letter and also the stickers with Jo and Clay.

Sticker front

Sticker rear

Clay 1971