Letter T Within a Shell On a Pair of Vintage Japanese Earrings?

by Jessie
(Honolulu, HI USA)

What is the item?

A pair of 14K white gold and cultured pearl screw-back earrings.

Can you please provide all background information?
Recently purchased during an estate sale in Honolulu.

What are the markings?
14K W.G. The letter T within a shell (identical to Mikimoto's mark).

Where are the markings?
On the screw-back knobs.