#boxed set

For those unfamiliar: There were subscription services where they'd send you a box and index dividers then a packet of cards, and every month they'd send you new packets which you would pay for. "Stop at any time", the ads would say, but the cards were typically sent randomly, rather than by chapter, so you'd have to keep receiving cards for several months to get the #27 to fit between January's #26 and April's #28. (The big numbers shown above are the chapters, the card numbers of each were smaller on the back.)

Finding totally complete sets in people's homes or in thrifts/antique stores does happen, but you know many people were a few packets short. I believe I'm missing a set or two myself on my 'The Greenhouse' houseplant information box from 1978...