Sorna Watch AG was based in Grenchen, and had belonged to the Roskopf Association which eventually became part of the Fédération de l’Industrie Horlogère Suisse (FH) in 1982. Not much information is currently known about the brand. According to a WatchUSeek forum member, the original company went into liquidation on October 17, 1994 and was shut down by January 8, 1996.
Jacky Ickx
Sometime in the early 1970s or 1980s depending on the source, several versions of a Sorna Jacky Ickx chronograph were sold under license through Heuer‘s Easy-Rider sub-brand. This included a bullhead style chronograph (ref. 2651) that featured a gold or black coated stainless steel case and came with a red or black dial, and a version with much beefier stainless steel case and a world timer-style dial (ref. 2692). Only the Belgian driver’s name, printed signature, and Easy-Riding branding appear on these dials with the Sorna brand name only appearing on the case back.
References
https://www.watch-wiki.net/doku.php?id=grenchen&s[]=sorna#google_vignette
https://www.watch-wiki.net/doku.php?id=heuer_easy_rider&s[]=sorna
https://www.watch-wiki.net/doku.php?id=roskopf_association&s[]=sorna
https://www.watchuseek.com/threads/sorna.44762/
https://www.timeline.watch/watch/sorna-bullhead-jacky-ickx-easy-rider/
https://drouot.com/fr/l/21654207-sorna-jacky-ickx-easy-rider-bl
https://curator.org/item/b85da06e9cebafc4957eee21fcdaff0a
https://curator.org/item/40c7a8fde816b48c89e245501bd2b57e
https://curator.org/item/b3daae0213cb23a191e12bb246790dd4
https://uhrerbe.com/unt/37095-jacky_ickx_easy_rider_chronograph_bullhead__date__vergoldet__handaufzug__kult.html
https://curator.org/item/3d9d168b4855ef9ab963099bec4ca8dd
https://timeandtidewatches.com/the-sorna-world-timer/