Roselane Antiques has dated this piece to the 1940s.

The Tanzanite is surrounded by a truncated Halo of brilliant cut diamonds.
Rectangular tanzanite 10 by 8 mm and 3.00 carats.
5 baguette cut shoulder diamonds approx 0.50 carats.
40 round cut diamonds surrounding the Tanzanite approximately 0.9 carats.
Weight 6.5 grams
Roselane Antiques has dated this piece to the 1940s.
You can view the stock and full dealer information on the Roselane Antiques Profile Page