IIRC the Brass Supers would have had a small round knob muffler not a baseball bat muffler. It is possible that it may be a Lud-alloy shell aka aluminum. Nothing wrong with that they sound great too, but not worth the premium of brass. They did make the aluminum shell ones without serial numbers too. Serial numbers didn't go into effect until about mid-1964 and the baseball bat muffler came out sometime in 1963, as did the alloy shell supras. The seller probably did the old magnet test and determined since it doesnt stick it must be brass. Well magnets don't stick to aluminum either, so make sure you do your homework before plunking down the cash on something that is advertised as brass and that may not be. If you can see the drum in person and you have a later supra already, you can bring it along for weight comparison. Brass will be much heavier. Also, if the seller will let you, remove a head and a lug and gently scrape the inside if the lug hole with a pocket knife or file. If the filings are silver, its aluminum, if its brass colored, well then....its brass. This would be the only true way to tell. If it's ebay, see if the seller will do this for you and show you pics of the hole after it is done. Brass color=brass, silver=aluminum. If they won't....I'd move on if you have your heart set on COB....if you can live with an early Supra that is aluminum and you get it for a good price, then go for it.