Is that old grey looking slug that you pulled out of the resistor plug made from a material that provides resistance and the copper you put in it's place is done to deliver no resistance?

I wonder if you could just fill the cavity with silver solder?
We are having difficulty finding the non resistance plugs here for a sane price...also have driven to the city only to find out that the parts guys computer tells him he stocks the ngk bp5es for the 420sel, but then he comes from the stock shelf holding bpR5es. The R stands for resistance plug. Strangely the computer also tells him the bpR5es plugs are 4.99 for a package of 2.....but the package he brings me is a molded plastic case with 2 spots but only one plug in the package....guess they are 4.99 for each plug...with a bonus invisible plug.