I assume they only built and sold them to get rid of the leftover stock and when the stock was gone Duplexes were gone (although Grossman still uses the name on many products). They sold them through their catalog for a few years, but they never sold many drums . . . they are really very rare. Everyone wanted the "name brands". Most people probably thought the Duplexes were just like the "Japanese blue sparkle junk" sold through so many catalog vendors. If people had know how high a quality these drums were they may have sold better, but by 1970 there were big changes on the horizon as “Made in Japan” would soon no longer equate to JUNK . . .