DSC mystery sensor

I have an old DSC Power 832 alarm system installed in my home and all over the home are these small round peep hole looking sensors - does anyone know what these are? Motion sensors? Would they be compatible with an alarm.com system after appropriate take over module installation? See photo.

Hmm. Bit of a head scratcher.

Kinda looks like a photo sensor. Have you pulled one from the wall?

I haven’t pulled one out of the wall. I guess I can… I’ll see what I can do and follow up…