Tom - I've had a few of that model and never saw or had the need for that spring wire in any of them. Looking at mine this morning, I can see no reason why it is there. And that one having survived for so many years indicates the base plate was very rarely removed, if at all. Tis indeed a mystery.
I see the spring listed as Part #39 in a few places but no information on what it is for.
Tom, when I looked at the spring in the parts diagram, the wrench was right next to it and I thought the two had something to do with each other. (which we now know it does). This is one of those things that you can't see the forest for the trees LOL. I stared at mine until I was blue in the face and just couldn't see it. Here is a snippet of the "Wrench Storage".
A forum community dedicated to router and woodworking professionals and enthusiasts. Come join the discussion about different types of routing and routers, shop safety, finishing, woodworking related topics, styles, tools, scales, reviews, accessories, classifieds, and more!