The picture at snake's link.
A piece of steel 3/8 of an inch thick x 4 inches wide x 4 1/2 feet long.
.375 x 4 x 54 = 81 cubic inches x .2904 lbs/cu in = 23.5 lbs, if I did that right.
He cut and ground a lot away in the shaping, but it still must have been heavy. Of course that’s not a problem for Jackie Chan.