Do you mean from the front or the back? If you're scanning scores of 70s chronographs that aren't explicitly labeled "Valjoux 7734", you want to zero in on the ones that are bicompax with a date at 6. Preferably, you want to see 15/30/45 printed on the right subdial. Preferably, the date will be in black, and resemble the gen font. If you can't make out either of these details, you're taking a very big chance!
If you're looking at a picture of the movement, orient it so that the V-shaped chronograph bridge is pointing down. The minute recorder is on the right, partially obscured by the bridge. Count the number of teeth on one third of the gear. (This is easier than it sounds.) If you counted 15, you're good to go.
And, yes, the chronograph will work. However, the minutes indicated will proceed in this sequence: 0,1.5,3,4.5,...
EDIT: Well, there goes modelizer explaining things with pictures again!