Interesting note: this card received an errata to include Pokemon with 70HP.
From PokeGym:
Mt. Moon
* Mt. Moon should read: “Any Pokémon (both yours and your opponent’s) with maximum HP of 70 or less can’t use any Poké-Powers.” This errata replaces text of “less than 70” with “70 or less”. If a Pokémon has a maximum HP of 70, that Pokémon cannot use a Poké-POWER while this Stadium card is in play. (Oct 1, 2004 PUI Announcements)
epicmedic
Interesting note: this card received an errata to include Pokemon with 70HP.
From PokeGym:
Mt. Moon
* Mt. Moon should read: “Any Pokémon (both yours and your opponent’s) with maximum HP of 70 or less can’t use any Poké-Powers.” This errata replaces text of “less than 70” with “70 or less”. If a Pokémon has a maximum HP of 70, that Pokémon cannot use a Poké-POWER while this Stadium card is in play. (Oct 1, 2004 PUI Announcements)