[patrickrd]

This picture is disturbing. How does it look like perfect continuous diagonal lines on both the pinion gear and the driven gear, and normal spur elsewhere? My best guess is that these are normal spurs with a little groove in the middle of each tooth... I have seen that before but I still can't see it looking like perfect diagonals in the picture.

If you look closely, you can also see that if we did assume they are helical gears, then the helix angles of the two gears would not mesh! One of the gears would need the angles reversed from what is shown.