I think if you can find a buyer, you will be lucky.
Old encylopedia have almost no value.

The 11th edition is the one collectible edition, if it has the calf leather, BUT, like Linda said, it's very difficult to sell. Having said that, I buy them cheap if they still have the original wood bookcase, because they sell really well as magazine stands.

http://en.wikipedia.org/wiki/History_of_the_Encyclop%C3%A6dia_Britannica#11th_edition

That one and the 9-10th edition are superb pre-WWI reference sources for writers and scientists, but not extremely valuable.

If it's a 1929 Sears printing, it's perhaps the 14th edition, still a good reference for early modern things.

The trick is advertising it as a reference source for WRITERS ... I've sold several ratty sets of encyclopedias bu focusing on their status as "state of the art" for people who write about history and write historical fiction.