Those are ground (shunt) signals. They are missing the actual semaphore discs, which were attached to the "spider arms" and were rotated through 45 degrees or so. A different manufacturer but similar idea (most such signals would have a red, rather than yellow bar however):
http://www.railsigns.uk/photos/p_ie1/p_ie1.html#pic_iedy
You can see the spectacle glasses are mostly missing (only the green one on the left still present)
I'm sure somebody with encylopaedic knowledge of signals will be along to help with the details. I'm out of my depth with all that stuff.