I think there were two ways to make that kind of bird beads in those days.

1)trailed decolation type (without carving)

size:normally samll
color: black
bird and sunburst motif easily go out under ground.

2)inlay type (with carving)

size:from small to large
color: black and transparent dark blue
(transparent dark blue bodies are rare)

Following pictures are type 1) (without carving)
All beads are authentic, no doubt at all.
One strand became deeply iridescent.
Another is a little bit iridescent.

I picked up one bead with beautifull iridescence.
The motif has already gone.
You can see the rest of motif.

type 2) is comming later