Andy Dingley schreef
The density is probably the best guide. Hard maples have a specific
gravity over 0.55, soft maples below this (total range is about 0.45 -
0.65).

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And this should be valuable in practice because ...?
Also you forgot to specify OD or green.
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Although there's a correlation with species, there are no
single "hard maple" or "soft maple" species. Sugar maples are hard,
red maples soft. The rest are variable.

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Actually it is simpler:
Acer saccharum yields hard maple (also Acer nigrum if this is acknowledged
as separate from Acer saccharum)
Acer rubrum and Acer saccharinum yield soft maple
All other maples yield maple (with or without a specifier)
PvR