No idea what to look for on the outside to get that there was this curly aspect on the insideAny maple can have curl in it.My understanding is that it is a genetic defect found in a small % of trees.I cut and milled a silver maple last fall that had nice curl from top to bottom.The very bottom of the trunk had the best with some quilt.I've also seen nice flame in red maple,but sugar maple is mainly what produces birdseye.
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