Your research concurs with mine. The catalog showed the clipped fins all the way through the last year in 1984. I've seen examples that weren't clipped, but have no idea when they stopped. 1974 was the last catalog year it had the silver fin can and NC.

As for personal experience with the Quasar, I liked all varieties of it in the catalog, but never bought one. It began and ended life costing more than the Alpha III, but for the most of its run, had the same catalog price.

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I love sanding.