Vintage Huge Lucite or Plexiglas Pendant With Silver & Enamel Landscape

This pendant is very different from most other lucite pendants with things embedded in them and dating from 1950s-70 in that:
1. It's very big and rather heavy
2. The metal looks like sterling silver
3. The red circle looks like enamel
It has a good level of artistry to it even though the palm tree sort of brings it down closer to kitschy imho, but it could also be referencing something else that has escaped me so far. Everything is well finished and I don't even see mold marks. It is not signed and I have not seen other pendants like this, so any help or information fellow collectors could share would be appreciated, such as whether metals and enamel (not shells, bugs, or dried flowers) were embedded in Plexiglas or Prystal, for example. I would also love to know how others safely clean this type of jewelry that has darkened or yellowed with age (it seems to be the case here).