GOOD FIND! I've never seen one like that.
As far back as the late 1950's there have been curved arm loaders on Ford N series tractors, those were actually made out of bent and welded pipe and had a lattice work look to them. Many of them appeared to have been made by farmers and often had a 'trip' bucket instead of full hydraulics. I can't tell for certain, but it looks like that uses a manual trip bucket system on the tractor in your photo. As the Ferguson was a near twin of the Ford N series, it makes sense to see a similar loader as would have been seen on the Fords.
In the late(?) 70's or early(?) 80's in Japan, Shibura used curved arm loaders on their tractors, they manufactured tractors for Ford and still make them for New Hollnad.
For some reason the curved arm loaders died out and high profile dog-leg style loaders became prevalant on AG and CUT size tractors. At the same time that high profile (low visibility) designs dominated the AG and consumer markets, the industrial loaders and industrial TLB units were shifting over to LOW profile steeply raked loader arms that offer even better visibility than the best of today's curved arm loaders.
Todays commercial TLBs (like Case, JCB and Volvo) still use the low profile arms and are a dream to use. The attached photo shows a modern JCB with its high visibility steeply sloped hood and its low profile lift arms. Logically we should see CUT loaders evolve to something similar to this in time.
