accurate instruments model 257 tube tester dial value

[Eevee1]

I have a accurate instruments model 257 tube tester that has I dial that the needle and tension spring need replaced, I am planning on replacing the dial with one of identical electrical value, however I cannot seem to find the dial value on the schematic. Does anyone know the value of the dial/ how to replace the tension spring and the needle and where to find a needle and tension spring? Any help would be appreciated.