Are the bowls for Crown Green Bowling weighted differently from those for flat greens?

"Forcibly" removed from upland East Lancashire as a youngster for family economic migration to England's South-East corner, I realize – to my shame – that I don't know the answer to this question. It got posed me by an old, southern, gentleman bowler. I remember the jacks were different, too : far bigger, yes, but were they weighted as well?.