It's also interesting that with all the different styles, box 11 for model 27 (VS) is by far the most common. I think Singer was making changes quite fast and then got to style 11 and settled there until they stopped offering the wooden box.
My next challenge is to collect manuals to go with each one, and research dates to see if I can get a good idea of what years each style was offered. It does appear that they change to the wire bobbin holder was to accommodate the bigger bobbins for the 15 with the bobbin case instead of the early IF that had the long beak shuttle, and did not use a bobbin case.
And it's obvious that the style 9 and earlier were for fiddle base machines. The very early VS machines have a narrow slide plate, so box 9 is the first one that would NOT work for the very early VS machines. And 10 and on are for the rectangular based machines. I don't know when Singer switched and started referring to that machine as model 27.
And this is why sometimes you'll see a puzzle box that sells for way more than most - it's one of the rare, early models. Though most often when a puzzle box sells high - it's because there is a rare, non-puzzle box attachment tucked inside the box. It's rare to find a "complete" box, and it's also common to find them with non-standard attachments included. Many sellers have no clue, and think their box is "complete" because it's got a lot of items. I've seen some that had almost no puzzle box parts. Looks like someone had used the box to put all their 66 attachments inside. Singer has stopped using the puzzle box by the time they came out with model 66.