Hi JoD,
The 30% is synthetic rubber and the 70% is natural rubber so the material is a blend of natural and synthetic rubber which means it would be a good quality and very durable material. There is more about natural and synthetic rubber in post #2 here. They use a variation of the molded Dunlop process.
In addition to the rubber itself (either natural or synthetic) … all foamed latex also includes other substances that are a necessary part of the compounding formula to foam and cure the latex so outside of any fillers that are used … a foamed latex core will generally contain about 90 - 95% natural or synthetic rubber (see post #8 here).
As far as I’m aware … with the exception of one small latex manufacturer in Guatemala … all the molded Dunlop latex you will find anywhere in North America is made somewhere in Asia (most commonly Sri Lanka, India, Viet Nam, Malaysia, Thailand, China) so this wouldn’t be a concern for me. The only Dunlop latex made in North America is continuous pour Dunlop made by either Latexco or Moutaintop foam.
I personally would have no issues with the quality or durability of their latex.
Phoenix