I'm fairly certain it was done both ways, depending on the railroads capabilities.

My understanding, if I'm remembering right what I read a long time ago, was that 5-ET was basically the same as the 6-ET in function and presentation, but all connections were pipe and unions instead of the 6 having the convenient pipe brackets to attach each valve to. This may be why no one can find any material info on it because otherwise they were essentially the same.

Scott