The quilting guide slips behind that three prong holder next to the tucker - slip the curved flat part underneath and the long part sticks straight up - and gets in the way of the ruffler when you go to close the box. That last thing in the row is the shirr plate for the ruffler, and it tucks under the ruffler in the box.
Your box is VS - Vibrating shuttle (or long bobbin) the box for the 15 (Improved Family) has a holder that looks like two wires for slipping round bobbins on. The 24 is the chain stitch machine and the attachments and box (inside) look very different.
Puzzle boxes were standard issue for SINGER machines of that era. I believe Greist was working for Singer (or closely with them) at the time. Not long after that they parted ways.
http://needlebar.org/main/puzzles/index.html