The only difference I can see is that the rear entrance to one of the landing bays on the original had a back-lit photograph of the interior of the bay placed a few inches inside the entrance. Jim didn't use this photo but built a forced perspective illuminated interior inside each bay. Both models have the tiny sequentially flashing landing approach lights. Removable access panels reveal the interior of the model filled with fiber optic strands, transformers, flourescent lights for the engines, cooling fans and circuit boards. This allows the model to be positioned for filming from different angles.
Wood framing inside supports the styrene skin.
I met up with Jim again at a recent sci-fi convention in Orlando, Florida. He had recently completed a model of the Cylon tanker. Jim graciously allowed me to photograph his models for the readers of this web site. Rare photo of the underside of the Galactica model. Of course, knowing what a stickler for accuracy I am, he dared me to build one exactly the same as the original shooting miniature.