Ricoh D096 Service Manual page 119

Other Replacements
The gears are numbered 1 to 12 in the order in which they are to be installed in the gearbox.
These numbers show both on the gearbox and on the front (exposed) surface of each gear.
If the gears fall out, start by finding gear number 1 and installing it onto location number 1
(setting it into place so that the side with the printed number stays visible). Then install the
remaining gears (2 to 12) in the same way.
SM 4-57 D096