Memorial Grounds was the home stadium of east London football club Thames Ironworks from the beginning of the 1897-98 season, until the end of the 1899-1900 season. The team continued to play at the stadium, under its new name of West Ham United, until they moved to the Boleyn Ground in 1904. The Memorial Grounds stadium was situated at the east end of Memorial Avenue, Plaistow, close to where West Ham station now stands.
You are looking for a traditional 35mm film canister containing a logbook and a couple of small pens.
Cache is available 24/7 but note it gets really dark in the evening time. Bring a flashlight.