The $12,000 price was for one menu, which you do not have. It was sold by Christie's in London last December, the Dinner May 20 menu, which is a very large, almost one meter long, piece.
The Proclamation is more common, I have seen several sell for $1,000 over the last year. The smaller size menus such as yours are worth $3,000 -$5,000 EACH, depending on size, attractiveness and condition.
They are very rare.