Over the years, with the stone’s provenance in doubt, other theories as to its origin have been posited. For example, in 1931 a letter-writer suggested to the president of the New Hampshire Historical Society that the Mystery Stone was actually a thunderstone—“the most perfectly worked thunder-stone ever discovered” (Letter, Kenneth L. Roberts to Otis Hammond, July 31, 1931, New Hampshire Historical Society). Thunderstones are reputedly rocks that fall from the sky during lightning storms. Another more recent theory argues that it is a lodestone, used for navigational purposes in the 16th century as an alternative to a compass. Still other theories link the Mystery Stone to numerology, aliens, massive planetary shifts, or a worldwide apocalypse.
Of course, there is also the possibility that the Mystery Stone was a hoax, perpetrated possibly by Seneca Ladd himself. Since Ladd never made any money off the stone and garnered little fame for his association with it, the motivation for concocting such a hoax remains unclear.