Figuring out R-value of manufactured hearth pad

[Mrbreeze742]

Found a pad that I like on Craigslist. It is Flagstone, 1.5" thick. I have a jotul which requires R value of 1.1 I believe and there's no specs or brand name whatsoever on this pad. I haven't seen it in person yet as its an hour and a half away.

First thought, would a manufactured pad have a higher R value than flagstone itself? I was thinking of stacking cement board underneath it, but then the seller said the bottom appeared to be particle board, but wasn't sure. She sent me a pic of the base, and It's hard to tell whether its wood or something synthetic. Seems hard to believe a commercial hearth pad wood have a wood base! Sorry for the ramble! Any thoughts?

 

[begreen]

The bottom looks like particle board. Is there any brand name or other labeling visible on the bottom? There would need to be a layer of micore inside in order to raise the R value enough to qualify. If not, this is an ember protection only hearth pad.