Swastika Necklace Identification

[CJWensleydale]

Apologies if this is in the wrong area but I'm trying to identify this necklace which my friend found amongst her mother's jewellery after she recently passed.
It appears to be a female's necklace but with a prominent black swastika on what appears to be a mother of pearl background. On the back is a retaining bar with 'BERLIN' crudely stamped.
Has anyone seen the anything like this before? I'm guessing it's some sort of sweetheart badge that has been added to an ordinary necklace and I would be grateful for any information...