Interested in what the two-letter initial may mean. These earrings are marked "HECHO/ EN MEXICO. D.F." to inside of screwbacks.
Marked "NF/ 925" to lower part, with the last leg of the N joined to the "backbone" of the F. I understand this may mean nickel-free, though the mark appears to be a maker's mark as it's stylized in this way. Could also read RF or AF, but under a loupe it really seems to be NF.
I checked the "Little Book of" reference with the owl pictured on the front. Any help is appreciated!