Jay, if you get some twigs from the questionable, it would help. As said before, "box elder" has glaucous twigs toward the end of the branch tips. Usually on the last 1-3 years growth, this waxy coating easily wipes off. Twigs can be medium green, pale yellow, pink and even purple underneath the coating. "Bow elder" has fissured bark like an ash tree and a compound leaf structure, hence the other common name "Ash leaf maple". "Norway maple" terminal twigs have a milky white sap, more easily seen when breaking the leaf petiole from the bud. The bud scar with "milk up" in seconds. "Norway maple" also has fissured bark.
Your last picture shows bark more of a "platey" fashion. This trait is common of many, many maples. The large colored area of heartwood is common with several soft maples too. I wish you luck. Either way, a nice find.
Mark...