Quite a unique finding, in all senses of the word.
These are magnetic pinless white plated steel "bar pins" with adhesive.
The ones we still have in stock are the rectangular ones which are approximately 0.5x1.75".
The back of each has very strong magnets on it, while the front is a separate piece with adhesive on one side.
All you need do is peel off plastic cover to apply your design.
I had a lot of ideas for these --- my favorite being making tiny flowers from left-over thread and yarn, perhaps to match your shawl or scarf, and placing them on the adhesive. Of course, you could get even simpler --- the simplest being to scatter beads on the adhesive randomly; or you could knit a small "bead stew" piece and attach it. Truly the sky is the limit on creativity.
This is a white (thin layer of silver) plating which is also known as "imitation rhodium" and "silvertone". The advantage of the magnet is that it won't leave holes in, or smudges on, whatever it is closing!
Please note though: It is recommended that pregnant women and people with pacemakers not wear magnets.