I recently ran across three broad hatchets at a flea market. All had blades about 10" long, and seemed to be in good shape. The handles were tight, the blades were semi sharp, but as I sighted down the flat edge of the blade there was a slight curve of 1/6" to 1/8". Should there be this curvature in the blade? What else should I look for? How much should I pay for a broad hatchet?