That particular example seems to have a lightly built tang per customer request. Pasi normally leaves stacked birch bark tangs heavier for hardest use, and you can see from peening of mine own that he does even heavier.

But below is what normally lurks under that stacked bark, and distal taper as blade, so, circa 0.150"-0.200" thick. Quite strong where it matters.

I am sitting here thinking just how much time he spends with scissors cutting strips and squares of bark.