Hi,
Hungarian Assay Office offers historical import marks in PDF format.
https://www.aurumzaloghaz.hu/kepek/file/K18671937.pdfEZÜST (silver) is on the right.
ARANY (gold) is on the left.
The import mark with assay office letter within the mark (seen in your pendant) was used throughout Austria-Hungary Empire from
1872 – 1902. It contradicts the information found elsewhere (1891-1902) but this is the most reliable document I have found so far.
Meaning, your locket can be dated 1872-1902.
Regards