Antique Victorian 10 K Gold Locket Necklace

Stunning Victorian locket that tests to be at least 10K. Marked on back and what I can make out seems to read RND 0775 CT Back Front. Back of locket seems to have a bit of a dip in it. I tried to show it in pictures. On a 24” chain that IS NOT gold. Locket measures 1 1/2”