These were very common on the Southern Pacific and Santa Fe lines but as mergers happened, many of these signals began getting replaced rapidly. They are so unreliable that railroad companies sometimes they will replace the mechanism but keep the old 8 inch lights and bells!
This is the only photo I have of a Raco Hydraulic Mechanism. I bought it at an antique shop. I have no idea where exactly it was taken, but it was probably taken somewhere in Central California around 1980.