As far as is known,three sizes of model were made, 3 inches,6 inches and 12 inches.
Its possible there were a couple of others for very distant or close ups shots,although if there were they were not used extensively.
It is worth pointing out that the smaller 3 inch model was structurally different to the
other two.Certainly there were differences between the 6 inch and 12 inch designs,but not to the extent of the 3 inch model.I believe the 3 inch model was a prototype design for the series,and was featured extensively in the first episode of UFO (Identified).
Firstly the design had a much more semi circular upper perspex canopy,while the plate structure was very thin indeed.The lower canopy was not curved but was infact
angular giving a square appearance.This prototype UFO may have been originally built in all three sizes,but only the smaller version was featured in the series,the larger ones being of the final design conceived by Derek Meddings.How do I know only the smaller design was used?Because in order to get the motor into the conical section of the model,part of its construction protruded out of the top of the model.Its small size did,nt allow it to be fitted normally without affecting either its size or stability.Screen captures of this model are featured below.
