This section is from the book "Popular Law Library Vol5 Sales, Personal Property, Bailments, Carriers, Patents, Copyrights", by Albert H. Putney. Also available from Amazon: Popular Law-Dictionary.
Sales in market overt in England, offer an exception to the general principle that the vendor can convey-only such title as he himself possesses. As has been stated, the doctrine has no application in the United States. In London all shops in which goods are exposed subject to sale are markets overt, but in the country only such places are so considered, as are set apart by custom for the vending of certain goods, and all shops are not included. Even in London the shops are considered as markets overt, only for such goods as are usually sold in the shop. The shop-keeper himself is not protected from liability by this rule of law; it is for the benefit only of the innocent purchaser. A sale in market overt could not convey title to property of the kings, nor could a sale there made, protect the purchaser who does not buy in good faith. And the sale must not be made in a warehouse or where the shop windows are closed.