My volunteer friend at the CRRM called me tonight and related to me some other findings.
Most surprising was that the back of the "semaphore" paddles WERE painted black at one time. The other side was red. And the old Newton signals had the white boards removed to avoid confusion with the semaphores (but all the pictures I see have the square white boards in place). The appropriate semaphore paddle was to be on the engineer's side.
He will be sending me copies of the 1929 rule book pages pointing this out.
The bottom line is that the signals were changed several times over the life of the San Juan Extention.
And to put all this in perspective, all I am interested in is making Cumbres and Osier historically correct for the periods the Friends are trying to reproduce. Cumbres is to be a "late period" representing the 50's and 60's. Osier is to be and earlier period representing the 00's and teens.