This had puzzled me since it appears to be a mirror image of a once-standard American style of semaphore blade, and is a rather incongruous decoration to find in a suburban Dublin pub.
I’ve had a lot of traffic on this subject.
It was most certainly not a signal employed on an Irish railway.
While the full story has yet to be unraveled, the signal blade appears to be of a type used on railways in New South Wales Australia.
The other day, I returned to The Full Shilling for another inspection of the signal and a few more photographs (etc).
Special thanks to everyone who made suggestions and provided information and links, including: Donncha Cronin, Ken Fox, and Michael Walsh. See the following link for discussion of my original posting: http://forum.signalbox.org/viewtopic.php?f=7&t=7525