I am almost certain I remember a cattleya vendor selling mericlones of Jewel Box 'Dark Waters' and several other Jewel Box clones about 40 years ago when I first saw their catalog. At that time the mericlone process was fairly common and inexpensive. The first mericloned orchids were sold in about 1964. Jewel Box was registered in 1962, and 'Dark Waters' was awarded in 1965, so it could have been mericloned as far back as then. I don't think you can assume your plant comes from a never mericloned line of divisions. There were certainly mericlones out there in abundance as far back as your oral history goes.
The major ancestors of Jewel Box are Gur. (C.) aurantiaca, C. dowiana and C. (L.) purpurata, with small contributions of C. mossiae, C. (L.) cinnabarina and C. (S.) coccinea. Most of those are big, and only coccinea is truly small, 4 generations back . JB can bloom at smallish sizes, but it definitely has the potential of being a very large plant when mature.
Technically, of course, mericlones are divisions. As small as a single cell perhaps, but there really is no distinction.