Інженерні зразки, оригінал зі США.
Engineering Sample.
Для тих, хто розуміє що це.
Proto2 (P2)
Engineering Validation Testing (EVT)

Proto - the first attempt at functional hardwareOnce the initial drop test stages are complete, the hardware project moves into the Proto stage of development. This stage marks the first attempt at delivering a fully functional device with all the necessary hardware components.Although Proto-stage units feature working hardware, they are merely the first incarnation of it. This means that Proto devices can have significant differences compared to their mass-production counterparts.These differences can pertain to the outside casing, in some instances, or they can impact ports and connectors located on the inside of the device. This means that a Proto-stage device might be incompatible with mass-production parts such as screens or buttons.Because of their differences relative to the final product, Proto-stage units are often highly collectible. They are also difficult to repair, though, as a result of said differences and incompatibility with commonly available parts and components.As this development stage involves functional hardware, even more testing is required to ensure proper functionality and long-term durability. Because of this, factories have dedicated machines, known as test stations, which test individual hardware components and sensors within the devices.As a result, the Proto stage often encompasses two sub-stages, known as Proto1 and Proto2, to account for any design changes and alterations that may occur due to information obtained from test results.Proto1 and Proto2 development stage units often run the NonUI variant of iOS. This type of iOS is largely intended for hardware testing and is often used by Apple's hardware engineers and calibration equipment.EVT - Engineering Validation TestingThe next major step after Proto is known as EVT, an acronym for Engineering Validation Testing. This development stage primarily focuses on perfecting the hardware and ensuring that no hardware-related problems persist.Close-up of a person holding a shiny, reflective phone with a single rear camera and flash.
EVT prototypes of the iPod Touch 3rd generation featured a rear camera, which is not present on mass-production units. Image Credit: DongleBookPro on YouTube
The EVT stage can encompass multiple substages, which are designated numerically, such as EVT-1, EVT-2, and so on. These exist to account for specific changes made during development, which are not large enough to constitute a separate development stage.