Scott (ESSHUP) beat me to it.
I have several that are similar to the one you show. I worked in the electronics design and production industry for over 40 years. In my career I went from big electron tubes to pieces we could only see under a microscope.
Starting at the time when printed circuit boards for electronic devices were first beginning to be regularly used, we used pin vices to drill the tiny holes needed for the "thru-hole" small wires of small components used on prototype printed circuit boards. They were used in conjunction with X-Acto knives that cut the traces (conductors) on epoxy/fiberglass boards, with copper bonded/clad to one or both sides of the board. Basically, we used the pin vices as hand drills for really tiny holes. Most bits this size would quickly break in a power tool. In those days we often relied on dentist's bits, which were quite expensive, but they were really tough. We also used them with very small but expensive taps when we had to make tiny threaded holes. Here is an example of the size screws we were using.
Pin vices are still used in a lot of industries, from jewelry, to gunsmithing, to miniature electronics prototyping.
My guess is that those found in a tackle box were used to hold small hooks -- #8 to #14 for winding fishing flies.
Good luck,
Ken
EDIT: In conjunction with the pin vices, I use things called "Helping Hands." They've been around since at least the late 1960s. They have a magnifying glass, and a couple of "alligator" clips on fully adjustable arms. The whole thing clamps to a table, or it has a suction cup on the bottom to hold it in place. They are great for doing small work that needs a little more magnification than 20-20, and that needs that 3rd and 4th hand that are steadier than most of us.
Ken
