5123 is the header to the west of wall 5007. It is oriented N-S and was likely used to support 5007. The upper block shows holes/wear on opposing visible faces consisted w/ those used in conjunction w/ long cranes. 5123 corresponds with a similar orange tufo header (SU 5125) in Wall 5006. Interesting orange-grey header-stretcher effect likely visible on the southern face of the terracing wall.
SE wall composed of large ashlar blocks