Late Victorian mourning brooch

This is very pretty brooch, designed with small pearls on what looks like black onyx then set into a gold metal setting with a scalloped edge.
One tiny pearl is missing - it shows up clearly in the blown-up photo but is not noticeable when looking at the brooch.
The back of the brooch is clear and contains plaited hair, the back can be lifted out.
The back has a small ring at the top so the brooch can be converted toa pendant.

There are no markings so the brooch is believed to be pinchbeck.
It measures 4cms by 3cms.

Please ask any questions or for more photos.