The Mann is an old design featured prominently in the 1979-80 Star Trek Spaceflight Chronology, then adopted by the Star Trek RPG created by FASA, and featured in a few novels and comics. Supposed to be an early starship, entering service shortly after the beginning of the 23rd Century and being retired shortly after the Constitution class entered service. It bore the brunt of Klingon engagements in the early decades of the 23rd Century until the Baton Rouge entered service in sufficient numbers. Designed by Rick Sternbach (who would later design many ships for TNG, DS9 and Voyager)
The model was originally created by David Metlesits in 3DStudio MAX, converted to OBJ by Richard Mandel and I converted it to DAZ Studio format, as well as giving it a good look on Iray, and giving sensible names to the materials (it was all material001, material002 and so on).
Anyway, ready for non-comercial use, and neither David nor me care if you use it for kitbashing. Have fun!