Complex sentence: There is some debate as to whether both the Ju 390 prototypes were completed, since there are no known photographs of the V2, all existing photos of the Ju 390 having been identified as showing the V1.
Split into simpler sentences: There is some debate as to whether both of the Ju 390 prototypes were completed, since there are no known photographs of the V2. All available photos of the Ju 390 having been identified as the V1.