Antique Black Mourning Brooch

Antique Mourning Brooch in Black Lucite with a center of prong-set glass crystal rhinestones. It’s my opinion that few of the stones may not be original to the piece or may be losing some brightness. There is one crystal that is sunken in/slightly crushed but it’s hard to tell unless closely scrutinized. I am not familiar with the back mechanism and cannot get it to unlatch. I also cannot see that there is an actual pinhead end. Perhaps someone else may be able to make it work. So this brooch is being sold in as-is condition yet will still make a great piece to add to a collection or display. Approximately 2-1/2“ in diameter. Smoke-free home.