I used the search bar we have above, since I remembered Peter Bazar, President of Imperial-Deltah posting about the Deltah co, and whether or not they ever sold genuine pearls. The question came up because of a series of mergers from around the turn of the last century, forward.
Some period print adds can be seen on the Imperial-Deltah website, and refer to simulated pearls only.
Anyway, I'm not sure if he ever reached or published a conclusion. Yours are very pretty and seem to be in terrific condition. Thank you for the photographs!