Every year poppy wreaths are still laid at the memorial to 23-year-old 1st Lt Arthur L Brown of the US Army Air Force on the banks of the river.
On January 14, 1944, the New Yorker's Republic P-47D Thunderbolt developed engine trouble, but it is believed he stayed at the controls to avoid plunging into the town centre.
The plane is said to have crashed in quicksand and its main structure was never recovered, but the small relic being offered for sale on November 14-15 (a valve rocker arm) was found by Harold Forster at the time and has remained in his family since.
Auctioneer Chris Large said: "It is a piece of metal less than six inches long. Having researched the numbers stamped on it, we know it came from a Pratt & Whitney R-2800 double wasp engine. I think it might sell for around £100 but its significance is far greater than its monetary value."
Contact: 01270 623878.