~26" long wooden propellor for, most likely, a radio controlled, model airplane. There is a letter "K" stenciled on one face, near the bolt holes, and the number 10552 stamped in the bottom of the hub. A coworker guessed it's made of maple, but it seems very light for maple. May have been made by a company called Sensenrich. The one I found on ebay was asking $100.