it's a bit hard to say anything without seeing a photo, there are so many triangle marks.
For example, OTTO REICHART Co. New York USA (1920s- 1960s) is one possibility of many, whose mark is comprised mostly of triangles. Within a diamond shape (diamond as in the playing cards) - a triangle and opposite the triangle is what looks like a half triangle which is actually the "R" signature.
A photo would help.. If you can take some photos of the mark and the earrings, which sound deserving, you might like to get an expert opinion.
