Perhaps it was just an honest mistake on the part of an inexperienced seller. If so, he/she should take it back and refund postage fees. The 12" tessar type lenses are very common and fairly cheap.

Here is the page from the 1935 Wollensak catalog ( The tables says the 9.5 inch is for 6.5x8.5in format. Note where it suggests going up in lens size for portraits.