How to tell the difference between Zone VI model I and model II enlargers?

[badbluesman]

A friend of mine has one that he bought second hand but we can't figure out which model he has.

[Duolab123]

Model 1 has a single focusing column, model 2 has twin focusing columns. They have different lens boards too. Model 2 has a round perfectly flat lens board with 3 slotted mounting holes and 3 tiny holes to access the alignment screws for the lens board.