Errr - I beg to differ. It had me stumped there for a while, as I was looking around in Crux - to me the Jewel Box has a characteristic A-shape formed by its brightest stars, which I did not see in your image.
Rather I reckon you took a shot of NGC3766 (mag 5.3) just over the border in Centaurus - I have attached a CdC screen copy to about the same orientation as your image - I believe this is a better fit...