A few years ago i took some similar on a necklace to be identified at the Natural History Museum in London and was told they are in a general category of FORAMINIFERA though most are microscopically smaller.
At any rate its a term that can be googled, and there are many images (enlarged) online too.
if you discover a more precise definition, please share it!

These are proving to be elusive.

First photo are forminifera found in Sussex up to 18mm.

The next are drawings of forminifera by Ernst Haeckel. One disc shaped shell looks similar to mine, but the size is unknown.

I believe my discs are from the south Pacific. The necklace is strung in the style of necklaces imported from the Philippines in the 1980s.

not sure where it went, here it is again:

https://depositsmag.com/2016/03/30/fossil-collecting-at-bracklesham-sussex/

The disc shaped formenifera are called Nummulites.

I wonder if my discs could be something different. They are so perfectly circular, and don't have little chambers like the nummulites I see online. Could they have grown inside of tubes? Trapdoors of some coral creature? Not from the sea but from fresh water? Ack

Now I want to make some with polymer clay!
So sad they are so fragile. OTOH, a thing of beauty is a joy forever, and you've captured that in your images.

Well, so far no luck with a positive ID. I asked in a couple of shell collecting groups with no response, and a weird item group too.

It is possibly a nummulite, which is a type of foraminifera, but I haven't found any photos or species names. It looks very different than other nummulite photos I've seen.

Do tell. Please! Inquiring minds want to know! :^D

They are both Facebook groups. You should join, it's entertaining.

What is this? Antique, vintage, and unusual item identification

WTF?! Weird Thrifting Finds

Researching a different coral I learned about disc corals.

I found the Scolymia species which shares similar features to the white disc beads. Perhaps the beads are their skeletons.

If you look at photos of scolymia most of the examples are very brightly colored. Many of them are sold for aquariums.

I have not yet found white examples like the beads.

can we know the size of this disc, please?

Stefany, I've been struggling with this one. I was helping someone ID some 'mushroom coral' and realized my little skeletons might be coral too.

The aquarium specimens I see online look about 2 -5 inches diameter I think, sitting on someone's fingers, but juveniles would be smaller, yes? One species was attributed to Thailand. If you can find more, that would be great. Much of what is available is on aquarium keeping sites, and dealing with live organisms.

Google images of scolymia coral:
https://www.google.com/search?q=scolymia&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjlyLb3_uXUAhUM3WMKHbWpDgAQ_AUIBigB&biw=1157&bih=615#imgrc=3xkDHLapJhxNsM: