The Apple Security Research Device is a specially fused iPhone that allows security researchers to perform research on iOS without having to defeat or disable the platform security features of iPhone. With this device, a researcher can side-load content that runs with platform-equivalent permissions. The cryptex subsystem allows a researcher to load a personalized trust cache and a disk image containing corresponding content. A number of defense in-depth measures have been implemented that are designed to ensure that this subsystem doesnt allow execution on user devices.”]
Source: https://support.apple.com/guide/security/apple-security-research-device-seca7ff718d2/1/web/1