I believe this is a Mourning Locket, the hair goes in between the pieces of glass. The safety catch dates it to about 1890. The metal acid tests to sterling silver but I haven't been able to find markings. I've only take it apart once so they might be on the inside of the piece somewhere.
Is in remarkably good shape. Clasp is intact and works, glass has no chips or scrapes. The pictures can give more details. The item "Antique Victorian Double Glass Mourning Locket Brooch" is in sale since Tuesday, January 19, 2021.
This item is in the category "Jewellery & Watches\Vintage & Antique Jewellery\Fine\Victorian, Edwardian 1837-1910\Mourning Jewellery". The seller is "erki_6715" and is located in St Catharines. This item can be shipped to Canada, United States.