Morpeth and Egerton Docks opened in 1847. This bridge was marked on early maps and was shown to be a Hydraulic Swing Bridge on the 1928 OS map.
The bridge carried Tower Road over the western entrance to Egerton Dock. Tower Road crossed four movable bridges - this one, another across the entrance to Wallasey Dock, and two that spanned the entrance locks between Alfred Dock and the East Float. Tower Road became known locally as 'Four Bridges' - a name which is still apparently used today.
Most of the swing bridges in Birkenhead Docks were replaced by identical bascule bridges around 1928-31.
All of the swing bridges that I have found details and images for in Birkenhead Docks at that time were hydraulically operated bridges of plate girder construction. Old photogrpahs show most of them as having a double roadway with railway tracks laid in the surface and outside walkways.
The Scherzer Bascules in Birkenheada docks were built to a different design from any other Scherzer Bascules that I have been able to visit. Most Scherzer Bascules - including those crossing the Royal Canal in Dublin, the ones in the old Surrey Docks in London and the Stanley Dock bridge in Liverpool - are operated by a pinion wheel at the pivot point rolling along a rack. In the Birkenhead bridges the beam that is equivalent to the rack acts as a drawbar. At the bridge end these bars are attached to the pivot point and when they are drawn back through or under the motor room the bridge is rolled back on its 'heels'.
The Scherzer bascule has been replaced with a low level fixed span.