2nd gear is missing some teeth in the first picture.
This transmission has an aftermarket Limited Slip Differential (LSD) in the front that is visible in the 2nd pic.
In this photo you can see the empty half of the transmission case, you can see the shift selector forks in the 3rd picture.
Pictures of a complete GD chassis Subaru Impreza WRX transmission opened up. Gears are on the left side, center differential is in the middle, empty half of the case is on the right.