The point with coating is a mix of both more light and more contrast.
The T coating was invented 1935 by Herr Smakula on the Zeiss factory.
T stands for Tranzparenzbelag.
The idea is that a naked uncoated lens have about 4% reflection from every lens to airsurface.
From the beginning the coating was a big military secret and they did the best to keep it that way, but it didnt take long before others copied it, and some made their own versions.
With the best coatings today that reflections is brought down to about 0,25%.
Zeiss current coating is T*.
While the "chepo" variation sold in the US is MC(Multi coated)
Here is a 7x50 HT with the T engraving just above the Zeiss mark.
Here is a 8x60 HT that was produced in February 1936, one in the first batch of 20 binoculars with coating,but before they had designated it T. This is the only one known surviving example
Edited by www.technika.nu