As far as I'm concerned it was copper too. If it were brass I feel like it wouldn't contrast as much with the environment they were filming in.
That "Barge Climbing saber" While having the details of a graflex clamp, It looks to be all one solid piece. I do believe it was a cast of something with a nipple and a graflex clamp. I can't for the life of me explain the terrible paint job - considering the black on the emitter, grip and "booster" section, this could be a cast from late ANH era.