Complex sentence: It is also possible that Marquette's description and Russell's account were both accurate for their respective times, and that the image had been repainted at some point between 1673 and 1836 to revise its appearance and iconography.
Split into simpler sentences: It is also possible that Marquette's description and Russell's account were both accurate for their respective times. The image may have been repainted at some point between 1673 and 1836 to revise its appearance and iconography.