From The iPhone Wiki
Jump to: navigation, search

The PROD (PRODuction) tag is a bit value that denotes if the image/ticket signature is for production devices or not. It is present in the SHSH certificate img3 and APTicket. When set to true, the image is designated to be installed onto production and development devices. When the tag value is false, the image/ticket is only explicitly accepted on internal devices. This is enforced through iBoot's do_load_image(void); routine. The routine skips the PROD tag check if the device's fuse value is false.

This is to prevent production devices from running non-production code.