Hi Jim, the Gold magnet is N52, the Silver is N48, both actually stronger than the Marchon magnets, I sourced the magnets myself to fit the block that Deane had made years ago. The silver is the closest to the Marchon when set up as a standard stock chassis, so thats why it was selected for the Tomy chassis to race against the Marchon. for measuring you will need a 'gauss meter'.