From the May 1979 edition of the BMW Club Journal

[Gelandestrasse]

Just spotted a pre-G/S home build....

 

[The Other PaulG]

Thanks, that's an interesting bit of history.

 

[Posh Pete]

Inspired by BMW works ISDT machines of an even earlier period, no doubt. https://speedtracktales.com/index-of-isdt-events/isdt-1971-isle-of-man/

 

[charlie batty]

...excellent

 

[dr nosh]

There are some great photographs in that linked page.