Real deal. Likely Vitra. I don't think I've ever seen a US version with black paint on "contract" base.
The gold-plated Gucci buckles are gonna be hard to source, Leif.
Made in Denmark with Pirelli straps would certainly preclude any association with Pearsall.
Try asking Knoll? It might help to provide evidence that the chairs are authentic.
...and wax is sometimes used as the only finish.
I think waxing the arms is a good idea.
Old-timer's oil finish application protocol: "Once a day for a week, once a week for a month, once a month for a year
Profile contour does not appear consistent with Saarinen/Knoll to my eye.
Just scratching the surface of teak furniture market reports available on the web suggests that cost and availability
Telltale medullary ray flake suggests stained beech.