The D-4 class was designed by John Eaves as a earlyer version of the later D-7/K'Tinga class. This ship was planned for Vorok's battle cruiser in Star Trek Enterprise "Unexpected" but at the end never used.
design scetch by John Eaves (startrek.com)
This is the Klingon D-4 resin kit from Starcraft in 1/1400. It's a very fine detailed model with 15,3cm in length. The kit contains the rods for the bottom of the neck. I corrected this kit with very thin steel braces in front of the grills and at the end of the wings.