Reddit mentions of Safety 1st Small Object Choking Tester

It's regulated:

even though functional attachments to clothing, such as buttons and zipper pulls, are exempt from the “Small Parts” regulation, we recommend that you voluntarily test such attachments on garments up to and including size 2 to ensure that those children cannot choke, aspirate, or swallow those attachments.

A small part is any object that fits completely into a specially designed test cylinder 2.25 inches long by 1.25 inches wide that approximates the size of the fully expanded throat of a child under three years old.

Small object choking tester

Yes, parents know.

The children I work with at my preschool ("daycares" tend to have younger children) are 3-5 so they should mostly be over the putting things in the mouth stage of development... and if you have younger children/children who stick non-food things in their mouths you can always use [one of these] (https://www.amazon.com/Safety-Small-Object-Choking-Tester/dp/B0062TNEOC).

That said, I think I am a lot more comfortable with risks and mess than my administrators. I see a lot of learning through concrete experiences happening when we take little risks, like using marbles or a mechanical apple peeler. Similarly, I see pride and self-confidence in children when they climb all the way to the top of the play structure. What that means for me is that I really have to be on my game so that nobody gets hurt. I have to make sure I know what the child is already capable of, what new challenges they are ready for and that I will be able to provide appropriate supervision during the activity and mop up when it's all done.