Except for the very oldest bottles, real bottles will have 'state' approval logos cast into them.

The states certified that the bottle held a full quart and then the bottle manufacturer could cast in a logo letting the consumer know this.

An early way for the customer to be sure they were getting what they paid for.

Of course, scam artists could replicate these mark's, but it increases the costs of the mold.

I have bottles in my collection with 4 ot 5 state approval marks.

Later . . .

Jim