That's called an "Earls fork" suspension system on the front of that bike.
Lots of old BMWs from the 50's and earlier had that kind of front suspension system, they worked specially well with sidecar rigs. In fact, my oldest brother owns a Russian Ural sidecar rig with that kind of front suspension. Best thing about them is there minimal or no fork dive with such a fork when a person puts on the brakes, unlike telescopic fork suspensions on other bikes.
I saw a very similar bike in the 90's being ridden by a guy somewhere in the south bay near San Jose, but it was much racier set up.
I don't think this front suspension system was considered too seriously by the big bike companies as it most likely is heavier than telescopic forks. Never saw another Earls forked bicycle since then till this one popped up!
Thanks for posting its pic on the forum!
Chombi