As early as ten years ago, HTC and Motorola were called "Android Double Male", when HTC came out of G1 to G23, occupying half of the Android mobile phone market. In 2010, HTC launched the Desire Z's side keyboard phone, which pointed directly to motorola milestone 3.
Now more than a decade later, in some second-hand channels can often see HTC out of the "engineering machine". Among them, these three HTC Desire Z engineering machines can be described as valuable, each of which has an independent number at the bottom right of the screen, which is very close to the mass production version.
In the early days, HTC was still reluctant to design the "search key" and touch key, but completely abandoned the trackball. At that time, Android mobile phones also basically had search keys, back keys, MENU keys and home buttons, also known as the "four kings key".
If I remember correctly, the HTC Desire Z doesn't seem to have launched licensed goods, most of them are US versions, so there is a T-Mobile carrier logo on the screen. Of course, our domestic users are not cold to the full keyboard design, unlike the old United States, which likes to send and receive emails with mobile phones, so they have a special love for the full keyboard.
The middle HTC Desire Z also has a hole under the back, which is used to test functions such as signals, so it belongs to earlier engineering machines.