Indestro model 120 3 piece SAE ignition wrench set
This one had me puzzled for a while until I took a closer look at the catalog. I often see mis-matched sets of tiny ignition wrenches listed on Ebay that contain one or two of these wrenches, but more often I see these listed on Ebay individually - orphans in search of new homes.
I wondered why I never saw any complete sets that included the screw that held them together, like the earlier model 137 ignition wrench set shown in the catalog illustration here:

Indestro 137 Handy ignition wrench set - 1935 Indestro catalog pp 42
Note that the wrenches in the 137 set are stamped with the name of the manufacturer of the magneto they're designed to fit - Delco, Splitdorf, Eisemann, etc.
When I took a closer look at the catalog, it finally occurred to me why I never see complete sets of the later production wrenches that made up the 120 set. The reason is really quite simple: the 120 set was not secured as a unit with a screw, even though the wrenches were all punched with a neat round hole in the center. Instead, the three wrenches were simply stapled to a piece of thin cardboard, as shown in the catalog illustration here:

Indestro 120 3-pc SAE ignition wrench set 1959 Indestro catalog No. 55M pp 66
Note the catalog listing shows the sizes for each wrench opening, as opposed to the earlier 137 set, in which the wrenches were stamped with the names of the magneto manufacturers.
The catalog illustration omits the fine details, but each wrench is stamped "Indestro Chicago U.S.A." with the size of the opening also stamped on each end.
The answer, then, as to why these hardly ever show up as complete sets is pretty simple: once they were torn off the card, they could be easily lost.
Here's my 120 set. I did exactly what my grandfather would have done - I went out into the garage and dug around in an old coffee can and found a screw and nut to fit. Done.

Indestro 120 3-pc ignition wrench set (front)

Indestro 120 3-pc ignition wrench set (back)