Complex sentence: Tamron's M42x0.75 T-Thread didn't appear on the market until about 1962, and they referred to it variously as a T-Mount, T-Thread, T-Adaptor, or a T-400, but not as a T-2.
Split into simpler sentences: Tamron's M42x0.75 T-thread didn't appear on the market until about 1962. The company referred to it variously as a T-mount, T-thread, T-adapter, or a T-400, but not as a T-2.