This is an adapter plate specifically for a Power HD TR-4 micro servo. It will allow the servo to bolt into a standard servo bolt pattern. The two servo mounting holes in the plate are sized to allow threading 3mm screws in to secure the servo to the plate. Servo is positioned to put the output splines approximately where they would be with a standard servo bolted into the same location (its not exact, might be off a little depending on what standard servo you compare to).
An example where this can be used is in something like a VP Phoenix for the shift or dig function.
The author hasn't provided the model origin yet.