In the repair forum a few people said they had not seen the special movement holder that Waltham provided for assembling their 1892 model 18-size movement. Here are a couple views of the holder. One side is for the top plate where you are advised to assemble the gear train and then place the pillar plate on top. The other side of the holder is sized for the pillar plate, although it does not have a cut-out for the setting lever, nor does not have accomodation for the fourth wheel arbor.