sometimes you can use needles to move the mechanism around.

You might also be able to see the locking sys with a light and a magnifying glass  to be able get a better grasp.

These things are fun to toy with, typically pretty easy to pick.

If that doesn't work, be sure to check that the screws holding any of the parts are not on the outside- some smart people actually install them that way. Even funnier, one of my old design boards at school had a padlock securing the two/three drawers- the sys holding is all together was a latch which went over one of those screw/hole dealys, screwed into one of the drawers. So, you could basically take the lock and twist it counter clockwise a few turns until it came out. Heh.