No it's a megaphone, by the Locks, for hollering to ships / tugs that were manouevring into the Alfred Dock / East/West float lock gates I think! Didn't have walkie-talkie radios back then...?!!
When working in the area I used to sit in the car and have my lunch just there - long before the fences went up. The Lock Master would shout instructions through the megaphone to the tugs assisting vessels in and out of the locks. It was still in use in the early 1970's.
Looking at what would be the mouthpiece end, it doesn't strike me as being big enough to shout through, most old megaphones I've seen normally have a larger mouthpiece, is it possible it was some sort of bugle call instrument.
God help us, Come yourself, Don't send Jesus, This is no place for children.
From memory Bert, the mouthpiece was about 3" x 2 1/2" and oval in shape. Looking at the photo again, it "looks" circular ? Maybe it was detachable ?? The Lock Master - in uniform too, definitely used to shout through it.
Good to see one of the I.O.M. steamers at the stage across the river!
Hmm! Could be open to abuse if the mike is on the end of that wire. Must have a secret switch somewhere! 'Left hand down a bit, Number 1!' 'Left hand down it is, sir.'