What bootloader/recovery firmware can it be? I have a Wiko Jerry phone, after some bootloader install has already happened on it.

Volume down + poweron gives this:



It looks like some test firmware, but it has no name/version info.

What is that?
As comment says, it is the factory test firmware of this specific model (wiko jerry 1). There is no documentation, or practically anything for it. It is used mostly by the manufacturer, to initially test/setup the device after production; although it is also an useful test tool in the case of mysterious hardware problems.