Japanese site emuonpsp reported today that a combination of keys was
found in the settings menu to display some hidden information about the
firmware installed on your Playstation vita.
This menu contains
information about the system build, repository, revision,… doesn’t look
like it’s super useful information for now, but still interesting I
guess.
The combination to get this menu to show requires practice but I could confirm it works on my vita (Firmware 1.510).
Go to Settings > System > System Information
Press simultaneously RTrigger + LTrigger + DPad Left + Square for a few seconds
Release those buttons then immediately press the start button
tadaa, additional information shows up