There were no nuclear weapons in 1925; so anything that existed in 1925 is known to not be a nuclear weapon. (Moreover, anything built to a 1925 design isn’t one either.)
The smallest critical mass is greater than 1kg; so anything smaller than 1kg is not a nuclear weapon (though it may be part of one).
Nuclear weapons are made of metal, not wood, cloth, paper, or clay; so anything made of wood, cloth, paper, or clay is not a nuclear weapon. (Thus for instance no conventionally printed book is a nuclear weapon, which is convenient for maintaining freedom of the press.)
There were no nuclear weapons in 1925; so anything that existed in 1925 is known to not be a nuclear weapon. (Moreover, anything built to a 1925 design isn’t one either.)
The smallest critical mass is greater than 1kg; so anything smaller than 1kg is not a nuclear weapon (though it may be part of one).
Nuclear weapons are made of metal, not wood, cloth, paper, or clay; so anything made of wood, cloth, paper, or clay is not a nuclear weapon. (Thus for instance no conventionally printed book is a nuclear weapon, which is convenient for maintaining freedom of the press.)