USA TREPANG~ SSN 674~MARCH 1971~ARCTIC UFO PHOTOGRAPHS

The Submarine came upon the object by "accident," as they were in the region on a routine joint military and scientific expedition. Officer John Klika was the one who initially spotted the object with the periscope.

This obviously implies that it wasn't ours, and unfortunately doesn't explain the different objects seen in the pictures.

Top Secret claims that on one of the pictures, there were some inscriptions.
I don't have a version of this, and it is too faint to see on these photographs.