Another percolator
 

This time our old Sona (from 197?) which we have been using again since Christmas. It had a "keep-warm" feature which was simply a 40 watt (approx) element, looped around the base and wired across the thermostat contacts - so in series with the main element when the 'stat opened.
Today the small element went o/c so I have removed it.

We thought (briefly) about buying a new replacement but found that in about 2015 it was decided we must not be able to keep coffee warm for longer than 40 minutes - so not much point.

Pictures attached in case anyone can provide a more exact dating - I won't bother asking for a spare element...

Re: Another percolator
 

Thinking about it - maybe the word "element" is incorrect since it may have been mostly acting as a dropping resistor for the real internal element and its heating effect might have been incidental.