Interiors, always with the interiors some people.
One thing i recall from watching old episodes on tape that i begged or bought
for referance that the one shot of two live action actors seen
through the windowws on a model is that they just couldn't fit in there,
watch for that shot if you have an ep with it, look closely and think about it,
you'll see what i mean.

This me and my friends later called the Gerry Anderson Continuity Problem.
To put it another way, the live sets occasionally bear little relation
to the models and vice-versa. As to scale, looking at the pod door for example
and comparing it to the size of a human in the full size interiors
makes this model about 24th scale or within the vicinity of that.
So a couple of 24th figures were converted to Alpha astronauts and moulded off.