thanks for the information Misha. Just to clarify some details re this piece,
No problem... it just stood out as being a 'maybe not' or 'yes, wise move'.
It happens to be the latter.
thanks for the information Misha. Just to clarify some details re this piece, and can confirm colour of rubberized insulation sleeves are plain green and plain red, and covered in fairly standard first half C20 woven fabric. Green rubber is without any wording, but printed in black along the red sleeve is.........(something) /M INSULATION - TO BRITISH STANDARDS - MADE IN GREAT BRITAIN - (then in black box) what might be BICC (then something else illegible). Whether this provides enough information to date the lamp I'm not sure.
Well, may have been to a Standard... but now it is not.
Rubber is suspect on anything old, especially if heat is involved. The lamp is a heater, unfortunately.
Green insulation is OK for Earth and nothing else. Likewise, yellow is another colour reserved for Earth.
Modern Earth conductor is a Green/Yellow, which is why the yellow is limited use at that 110/240V potential.
I'm currently rewiring this home where main cables are rubber insulated and a similar marking on the red and black insulation. I'd hazard a guess some of the code relates to rated voltage and stranding construction. The cables here date from the early 1950's... fixed wiring type though. I've rewired homes with older type cable from the 1920's. they had rubber and textile outer.... much of which was in very poor condition.
As you can see, the dome support arms are chromed as is the lower half of the bulb holder, although upper half (bayonet fitting) is simply a silver coloured metal.
As such it requires Earth, unless converted to operate at 'Extra Low Voltage' as you would power LED type lamps designed for 12V.
The bulb holder arrangement is without any facility (screw method as shown in your link) for attaching an earth wire. Obviously, the original intention was that the on/off switch was situated external to the lamp -
From what I can see, modern bayonet fitting lamp bulb holders appear to be plastic throughout.
Small hole.... perhaps enlarge and debur any such drilling work.
No means of connection.... modern light fittings use a large diameter lug fitted where threaded tube fittings mechanically assemble the fitting... granted, these are located within wiring chambers in multi-lamp arrangements. perhaps there is an option of making a solder type connection within the lampholder or at the place this holder screw clamps to the glass base.
Yes, modern are all plastic and so, no need for Earth - double insulated.
Smaller cables are available for that tight entry. They are smaller by virtue of higher grade insulation, not smaller conductor. They are often PTFE with glass brade over insulation, and used in halogen lamp connectors, due to higher heat tolerance. You also see smaller cable of aesthetic value used in crystal chandelier internal wiring. Such cable would need to be joined with the plastic/textile lead though.
Perhaps there's no need for an earth, provided the on/off switch is placed away from the lamp, meaning no need to actually touch any part of the lamp.
See, the lamp could develop an Active [live] to frame fault that looks like a blown lamp... it could be 'on' when a lamp change is attempted. Likewise, an Active to frame fault could develop that doesn't take out the light but still energises the frame. Incidental contact to support arms being Live.
This is going to take a fair bit of fiddly work to Earth proper, and unfortunately an in line cord switch doesn't negate the need to Earth it... only Low Voltage conversion will negate that need, or more to the point hazard risk.
Good luck with it though.
Lovely big piece... I'm a sucker for the light play that comes from the prismatic diffusion effect of good crystal glass.