Mirror universe
(coexisting on another dimensional plane)
(coexisting on another dimensional plane)
A Project 705 class submarine
The Project 705 (or Alfa-class) was a type of military submarine used in the mirror universe on Earth during that planet's 20th century. One of these submarines was successfully seen torpedoing a Type VII submarine. (ENT: "In a Mirror, Darkly" opening credits)
Although not mentioned by name, the Project 705 submarine appeared in the opening credits, indicating the craft was manufactured and used in that universe. It was re-purposed footage from the 1990 Paramount Pictures film The Hunt for Red October, albeit flipped. The studio models for this movie, including that of Project 705, were built by Gregory Jein, Inc., subcontracted by Boss Film Studios, and for which Jein had to temporarily suspend his commissions on Star Trek: The Next Generation. ([1]; Cinefex, issue 42, pp. 10-21