These are antique glass floaters found in the fish factory in Stöðvarfjörður, Iceland. Once used by fishermen in many parts of the world to keep their fishing nets afloat. These hollow glass balls contain air to give itself buoyancy.
Norway was the first country to produce these glass floats around 1840 in Bergen. Most now originate from Japan. Usually are shades of green because the glass is from recycled sake bottles.
These glass floats from the past are now replaced by aluminum, plastic or styrofoam. There tends to be markings of origin but these have no clues. Possibly came from the other side of the world.?
I used glass floaters for CYCLES & CIRCLES: VERNAL EQUINOX RITUAL.