The D'Vahl is a cone-shaped Vulcan ship with "wings" on either side of the front tip, and three engine pods, separated by 120. The ship was in service during Earth's 20th century.
Gallery: Vulcan Starships The D'Vahl appeared at the end of ENT: "Carbon Creek" and rescued two of the three surviving crew members of the survey ship (below) that had crashed on Earth.
It is quite obviously a design different than the survey ship.
The model reappeared without changes in ENT: "Awakening" and "Kir'Shara", 200 years later (see below), where it arguably has to be a different design.
Two years later, the High Command seems to have pulled some of these vessels off the mothballs for low-grade duty, as we see them in the Vulcan trilogy in ENT: "Awakening" and "Kir'Shara".
I previously believed there were some modifications to the CGI model, but it is the same that was in "Fusion".
Two of these small vessels appear together with one ship of the D'Kyr type to attack Enterprise in Vulcan's orbit. A vessel of this type is also part of the "welcome fleet" in "Storm Front".
T'Pol and Archer spot a diagram of this vessel on the display device in Daniels's quarters in ENT: "Future Tense".
Considering the similarity to the Surak class, it shouldn't be commissioned too far into the future.
A label on the display, close to the depiction of the ship, reads: "Retro Fitted Dorsal Carrier, Design XRT-55D, Commission Date 3125".
This doesn't make much sense, and it could refer to anything else on the chaotic screen.
The Vulcan is a cold war icon; everybody's seen the old film footage of these bat-winged white shapes getting airborne with a howl of engines, pouring black smoke from their exhausts and carrying a bomb load of instant sunshine during mock scrambles.