Mamod Steam Tractor 1972 /Original Box & Moving Freely

Mamod steam tractor from 1972 (shown as toy of the year on the box 1972) in good used condition and untouched by me or cleaned in any way. All parts move freely and it seems complete except for the little funnel. I see no reason why this shouldn't work but it is untried as I am a girl and do not understand these things!! Original box which is scruffy.