Really excellent summary of the historical and modern observations, Scott! I was planning to include some of the history around Z Cen = SN 1895B in my article on Mina Fleming in the upcoming August issue of Sky & Tel, but that was cut in editing/tightening the length. In any case, you covered it in much more detail.
Here's my description of NGC 5253 from Australia through an 18" f/4.5 (JMI NGT split-ring equatorial) in July of 2005.
Very bright, fairly large, elongated 3:1 SW-NE. Very strong concentration with an intensely luminous 20" core. The outer extent increased with averted vision and faded at the tips, with overall dimensions of ~2.0'x0.7'. A very small bright knot is at the NE edge of the core and appeared similar to a nearly stellar nucleus (though offset from center), particularly using direct vision.
I would assume the "very small bright knot at the NE edge of the core" is the region of SSC #5 in Calzetti (#1 in Gorjian).
I only wrote down some brief notes from the view in Jimi's 48" that Akarsh just referred to, but I mentioned "Strong concentration with a very bright elongated core. At the NNE end of the core is a very bright elongated knot (Super Star Cluster #5 and HII region?)." I didn't note a stellar point (assuming the SSC is essentially stellar,) but Akarsh's sketch shows the feature.
Gorjian also combined "clusters" #1 and #2 to form a larger "section A" in some of his 1996 paper.
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