[Arran]

Roy;
It was the common practice, in the past to replace sections of a tapped voltage divider resistor if one section was open, by bridging the failed section with a new resistor, but at the same time you had to make sure that the old section wouldn't repair itself leaving you with two resistors in parallel with a net lower resistance. Given the vintage of this set it was probably a type of candohm wire wound resistor which was riveted to the chassis for heat dissipation. Opinions vary on what to do with these, some replace them with chassis mounted Arcol resistors, others gut the resistance wire out of the Candohm and reuse the terminals with discrete resistors, the third option is to mount a terminal strip and use higher wattage resistors then the originals.
Regards
Arran