Adaptable vintage necklace of imitation pearls probably in acrylic (lucite or similar) with transparent spacers and mounted on "memory" wire (memory wire was a military invention wire that began to be used in jewelry in the 60s)
The pearls have a ring around the hole due to the oxidation of the metal wire inside and the passage of time (see images). Otherwise, the pearls preserve the pearly coat quite well.
From the 60s decade
Attention, it is NOT gold or silver so it can cause allergies.