According to the Ebay description this is the spare camera nose dome for N6578D “The Psychedelic Monster” but was actually used on N7614C which came to the UK to make a film for BOAC to promote the Boeing 747 when they were first introduced. After filming N7614C was abandoned spending time at Luton and Shoreham before eventually landing up at Duxford with IWM.  ABpic link below includes photos of N7614C with the camera nose fitted.

Aviation photographs of Registration: N7614C : ABPic