Gear that is an S class boat.
Like Charon said.
The boat in question is one of the war build U class, very german looking conning tower but really only the British U class had that very short read deck with raised torp tubes. And only the war class ones had the well fitted deck gun.
I think only the old post war reprint of Janes calls these a V class...its the same boat as a late U but they ran out of U names I guess.
I guess if it happens to be one with a name that starts with V its a V class.