wrote:

On Saturday, 2 December 2017 17:15:00 UTC, D.M. Procida wrote:

The bulb contacts are riveted into a pair of ceramic holders; here's a
picture https://www.dropbox.com/s/2mscxp11nl3u4d3/IMG_0238.jpg?dl=0.

The lamp can be adjusted for height, and a section of the wiring was
this curly cable:
https://www.dropbox.com/s/oq3gep524s0es6u/IMG_0240.jpg?dl=0. It's
two-core, and what looks like the third core in the photo is actually
elastic, to accommodate the stretch.

2nd link is wrong one.

So it is - here is the curly cable:
https://www.dropbox.com/s/oq3gep524s0es6u/IMG_0240.jpg?dl=0

Why don't you just splice to the existing cable for the lampholders

That was the existing arrangement, and the splices, subject to years of
movement in the brass tube, was looking rather unhealthy.

Daniele