I cant say for sure it is without seeing it,but musclewood is pretty easy to identify by its distinct appearence....i have made a bow from it,which has since been retired now,but shot thousands of arrows
Heres what the back looks like,its been dyed a brown color,and i steel wooled the ridges after dying it to highlight the muscles.
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And here it is braced hanging on the stump from wence the bow came from
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If you look to the right limb tip there is an american hornbeam,and another one to its right