I found this stunner on the Cheetah website, after mentioning him in the El Rollo megapost.
It was built in 2016 and is, I think, a very rare 1930s Excelsior Super-X with a 1930s Koslow overhead valve conversion. Koslow OHV heads were usually fitted to Harley bottom ends. This is what the Cyril Huze blog says about Koslow...
'When in 1931 Ignaz Schwinn, the owner of Excelsior/Henderson Motorcycle Company in Chicago, decided to shut down the business, one of his engineers named Andrew Koslow, an active hill climber and owner of the closest franchise to the actual factory, had a plan. At the time OHV Excelsior big Bertha hill climbers Gene Rhyne (Crocker future engineer) and the legendary Joe Petrali utilized a twin port hemi head configuration. So, Andrew Koslow made up a new set of castings using the Excelsior top end as inspiration, and converted the big Flathead VL’s to use in the then popular midget car racing. Andrew Koslow ran his motorcycle shop through the 1930’s up until the early 1950’s but never built a complete bike!'
The bike was commissioned by Japanese street fashion/custom motorbike big cheese, Sin Takizawa of Neighborhood. It was built for the Born Free Chopper show, then converted to race at TROG, the Race of Gentlemen in California in 2016, but I don't know how it did in the race.