They are hand made / sculpted works of art, by the professional designers/artists who work at the Marx Toy Company in the 1960's. They are sculpted in a modelling medium, called plasticine. When completed, these figures would be used to create the steel injection molds for mass production. Look closely at the photos. The figures are much more detailed than the mass produced plastic figures.
I assume this is because some of the detail is lost when you go from handmade to mass production. The item "VINTAGE MARX PROTOTYPE INDIAN CHIEF & WARRIOR FIGURES 155MM" is in sale since Monday, May 08, 2017. This item is in the category "Toys & Hobbies\Vintage & Antique Toys\Play Sets". The seller is "k-tell-rec" and is located in Old Greenwich, Connecticut.
This item can be shipped worldwide.