July 1927 - No. 4 hydraulic coal hoist under construction at Penarth Dock being the work of the East Ferry Road Engineering Company Limited of Millwall, London. The original of this photograph is held at the archive of the National Museum of Wales. [Museum item number : 83.170I] [629]

In the middle image enlargement, note the vertical tie-bars and the brackets affixed to the masonry of the pier highlighted in blue. Mystery solved! These mountings are still in position as seen during my visit of October 2023 and are installed on the piers for Coal Tips Nos. 4 and 5. See also these tie-bar features in the technical drawings and specification within the Chapter on the subject of the Reconstruction of Three Tips - 1912 - 17.

October 2023 - In the lower image, note the mounting plate for the heavy chain seen in the main image above, although I am not sure what the purpose was of these chains - see red highlighted area. Also in evidence are the vertical quarry drill marks for splitting the stone dating from the 1860's. The Radyr Stone was known as a 'freestone' which meant that it could reliably be split in any direction without breaking. The green highlighted area was probably a bracket support for a walkway around the exterior of the coal tip also dating from the 1913 reconstruction. Also note the horizontal relief recess level with the top of this bracket which is probably to receive and align the walkway. [001]