The floppy felt headwear, made by New York milliners Madcaps, will go on sale at Nate D. Sanders auctioneers on Thursday(27Aug15), along with a picture of the actress wearing it.

A spokesman for the auction site says, "This hat originally belonged to Marilyn Monroe and was part of a sale of her possessions in 1999. Although items owned and worn by Monroe are rare, the value for her items is high primarily because collectors covet anything she has worn. The hat is accompanied by a striking photo by Roy Schatt of Marilyn wearing it."