I think maple is possible, but it is pure speculation from me. Maple trees are prolific in the Eastern US and Canada and many of the softer varieties grow quite fast, especially compared to other species of hardwoods like oak. Did Uncle Mats really need to import lumber from America or could they have sourced something closer? It would be nice to hear from someone who worked in the factory throughout those years, because even if you sanded it all the way down, I don't trust myself enough to positively ID a species.
I don't usually find a use for this smiley
, but I like so there you have it.