The bobbins are smaller and made of nylon. Both are the same and there's a bar slug that goes in one and the screws anchor in the baseplate and just project up through the other bobbin. The only thing that holds them together is the potting and solder on the cover. Once you have the parts in hand it's pretty self-explanatory.
Here's a link to a page with an okay picture on it. It's not the best shot but you'll get the gist.
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