All this data is potentially out of date, and should be taken with a truckload of salt
When originally introduced, the Bustard was a reskin of the Badger Mark II model. In 2006 it was redesigned to be a reskin of the larger type-3 Badger model, an orphaned model which had never been used in the game. This served to differentiate it from the Crane (which also used the Badger Mark II model) and to put the type-3 Badger model to use. This makes it one of the only uniquely modeled Tech 2 ships in the game, as it is not a reskin of a Tech 1 ship.
Note that in spite of the unique model, the ship is still considered to be a variant of the Badger Mark II for invention purposes.
Below are additional ships images. Click the image below for a larger version: