My R69 had the Earles Fork. it worked great.
Mine too Danny, they were primarily designed (not by BMW) to reduce the "fork dive" of telescopic forks, and BMW used them for many years before bowing to aesthetics in the early 1970's.
The modern BMW "Telelever" forks work in a similar way, but look more like conventional forks. Earles forks were long gone by the time the R90/6 came along, but lots of sidecar builders replaced their telescopic forks with Earles forks to add some much needed stability. Cheers, Terry.