doubleofive said:

The pilot Enterprise had a larger bridge module, larger deflector dish, solid red spiked nacelle caps, and holes in back of the nacelles. When they got picked up, they upgraded the model to have lighting, so they ended up changing all that. So there are really only two versions, they just used the pilot version in the series if they had a stock shot of it doing what they needed it to do that week.

They also used a few AMT model kits, but that's beside the point.

Actually, as I understand it, Matt Jefferies et al. made a few minor tweaks to the Enterprise model between the two pilots. Not nearly as major as what happened once the series was finally picked up, though.

And FWIW, I understand Jefferies wanted to go back to the solid-colored nacelle caps for the abortive 1970s series Star Trek: Phase II. These would have been gun-metal blue, as would the deflector dish. The nacelles would've been shaped overall like those of the movie Enterprise, though (i.e., flattened instead of cylindrical).

(Actually, even calling it a "deflector dish" is a major Trek retcon. Originally Jefferies meant it to be a radar dish, like on real-world airplanes. He even wanted, at one early stage in designing the Enterprise, to protect it under a nose-cone on the front of the secondary hull.)