Mine will hold a magnet. Now this is only the Classic. The Jets and original Gamemasters did not have them.
According to Jack, he put the metal rod in all of the classics. The black section of the riser is a special plastic formula that jack developed. He mixed it himself and poured it into the mold for the riser. Before he poured in the plastic, he inserted the metal rod.
There are so many questions that only Jack could have answered. The Jack Howard enthusiast lost more than a great bowyer when he passed.