Yes those are wire wound resistors that are commonly found in high quality instruments instruments that are far younger than yours. They were used for a long time in high quality resistance boxes and Wheatstone Bridges and such...... I do not think they are used much any more but are very good, very expensive resistors.
The connections on the box are one COMMON and then three progressively higher resistance connections for the three scales. I think you already know which connection is for which scale.
Looking at the non linear scale, I have changed my opinion. If you wish to measure about 1 K Volt I would increase the highest resistance (300 Volt Scale) to ten times this resistance (total resistance) with an external series resistor. This would give you a scale that would put 1 K Volts about in the middle of the needle indicator range and be easier to read.
If you do this use a
resistor rated for high volts. The total scale reading would be 3 KV and your approx 1 KV reading would be around the 50 mark,close to center.
Depending on the mA requirement for your meter, the power thru the setup could be maybe ONE WATT. So I would use a 5 Watt resistor. We do not know the mA requirement of your meter but we can determine it if you measure the resistors in the box. We can be more exact about the resistor Watt rating if we knew the mA full scale requirement of your meter.
Of course, be careful and make your connections solid with good insulation and distance them from any possible short.
For anyone following here is a simple summary for both moving coil and moving Iron Meters that includes calculations for series resistors for different ranges:
https://electricala2z.com/electrical-instrumentation/moving-coil-moving-iron-meters/