Matt from Ironwood Designs here,
Thought I would chime in on this discussion.
True, Mitchell did claim they were Teak, the stocks are not Teak.
We have used Teak for years to make our Yugo reproduction stocks, simply because it looks virtually identical, when finished with a typical gun stock oil, like Tung, Tru, or Linseed oil.
I had spoken to Bill at Patomic arms a few years ago about this very same question. He responded and said that the guys at the Zastava factory laughed when they heard that everyone thought that the Yugos came with Teak stocks, a very expensive Southeast Asian hardwood. The actual wood used on most of the M70s was a species of Birch, found in Eastern Europe, ( Yugolavia and regions nearby).
M90/95s were typically fitted with Beech wood, which we do use for both M70 & M90 stock sets. I'm not sure about Elm, as I have never worked with that material before.
Here's a pic with some Yugos with our Teak sets installed and finished.
Can you tell which one is Teak? One of the sets has original Yugo furniture.