Legal Question in Business Law in California

Re: items for sale

No. The sign is an invitation to do business with the seller and not a promise to sell if specific conditions are met. The same is true of other sale advertisements, including those which set a price and don't say "or best offer".

Re: items for sale

The phrase "or best offer" is almost universally understood by judges and legal scholars to be an invitation to make offers lower than the asking price, which the seller may accept or refuse at his sole option.

The law of formation of contracts long ago moved away from strict, literal and mechanistic interpretation of such phrases. A linguist or a professor of logic could argue that "or best offer" necessarily implies that if no offer better than 5c is received for the used Cadillac advertised in the paper, the seller has committed to accept a nickel. In 1700, the law might have agreed, but the modern position of the law (Say, 19th Century onward) is that "or best offer" is not that commital and merely expresses a willingness of the seller to consider offers lower than the stated price.