The yard i go to uses the same scale for shred, cast iron, HMS, auto cast. If you dont tell the scale operator or yardsman, They will pay you as shred.
Example.
Pull on to the scale. "Ok go ahead" they say.
Then I say I got all cast iron.
"OK. hold on....... Pull up to the 3rd spot on the left. yard guy will meet you there"
Even with copper and alum, make sure what they are paying you for. Who wants copper2 price when its all copper1