Is Armed with Proof legal in Standard, Modern, and Commander?

Armed with Proof is legal in: Legacy, Vintage, Commander.

What type of card is Armed with Proof?

Armed with Proof is an Enchantment. Its oracle text reads: "When this enchantment enters, investigate twice. (To investigate, create a Clue token. It's an artifact with "{2}, Sacrifice this token: Draw a card.") Clues you control are Equipment in addition to their other types and have "Equipped creature gets +2/+0" and equip {2}."