When did seth thomas stop making adamantine mantle clocks?

The Seth Thomas Adamantine finish was developed in about 1885. It was very popular so the method was used for over 30 years until 1917. The word adamantine means impenetrable and of course, in 1917, that is what was believed. Now we know that all finishes are penetrable, given the right agent. Seth Thomas has been making clocks in America since 1813. For more information see the Seth Thomas article at www.Placeofclocks.com, a registered Seth Thomas Dealer.